Publications by year
In Press
Bearhop S, Bodey TW, Cleasby I, Bell F, Parr N, Schultz A, Votier SC (In Press). A phylogenetically controlled meta-analysis of biologging device effects on birds: Deleterious effects and a call for more standardized reporting of study data. Methods in Ecology and Evolution
Bearhop S, Cleasby IR, Bodey TW, Vigfusdottir F, McDonald JL, McElwaine G, Mackie K, Colhoun K (In Press). Climatic conditions produce contrasting influences on demographic traits in a long distance Arctic migrant. Journal of Animal Ecology
Votier SC, Fayet A, Bearhop S, Bodey T, Clark B, Grecian WJ, Guilford T, Hamer K, Jeglinski J, Morgan G, et al (In Press). Effects of age and reproductive status on individual foraging site fidelity in a long-lived marine predator. Proceedings of the Royal Society B: Biological Sciences
Votier SC, Grecian WJ, Witt MJ, Bearhop, Attrill M, Godley BJ (In Press). Seabird diversity hotspot linked to ocean productivity in the Canary Current Large Marine Ecosystem. Biology Letters
2023
Lee SCR, Hodgson DJ, Bearhop S (2023). Correction: What has biotelemetry ever done for avian translocations?.
Mov Ecol,
11(1).
Author URL.
Soriano-Redondo A, Inger R, Sherley RB, Rees EC, Abadi F, McElwaine G, Colhoun K, Einarsson O, Thorstensen S, Newth J, et al (2023). Demographic rates reveal the benefits of protected areas in a long-lived migratory bird.
Proceedings of the National Academy of Sciences,
120(12).
Abstract:
Demographic rates reveal the benefits of protected areas in a long-lived migratory bird
. Recent studies have suggested that protected areas often fail to conserve target species. However, the efficacy of terrestrial protected areas is difficult to measure, especially for highly vagile species like migratory birds that may move between protected and unprotected areas throughout their lives. Here, we use a 30-y dataset of detailed demographic data from a migratory waterbird, the Whooper swan (
. Cygnus cygnus
. ), to assess the value of nature reserves (NRs). We assess how demographic rates vary at sites with varying levels of protection and how they are influenced by movements between sites. Swans had a lower breeding probability when wintering inside NRs than outside but better survival for all age classes, generating a 30-fold higher annual growth rate within NRs. There was also a net movement of individuals from NRs to non-NRs. By combining these demographic rates and estimates of movement (into and out of NRs) into population projection models, we show that the NRs should help to double the population of swans wintering in the United Kingdom by 2030. These results highlight the major effect that spatial management can have on species conservation, even when the areas protected are relatively small and only used during short periods of the life cycle.
.
Abstract.
Ozsanlav-Harris L, Hilton G, Griffin L, Walsh A, Cao L, Weegman M, Bearhop S (2023). Differing drivers of decline within a metapopulation has implications for future conservation.
Atkins K, Bearhop S, Bodey TW, Grecian WJ, Hamer K, Pereira JM, Meinertzhagen H, Mitchell C, Morgan G, Morgan L, et al (2023). Geolocator tracking seabird migration and moult reveal large-scale temperature-driven isoscapes in the NE Atlantic.
Rapid Commun Mass SpectromAbstract:
Geolocator tracking seabird migration and moult reveal large-scale temperature-driven isoscapes in the NE Atlantic.
UNLABELLED: RATIONALE By combining precision satellite-tracking with blood sampling it has been possible to use seabirds to validate marine carbon and nitrogen isoscapes, but it is unclear whether a comparable approach using low precision light-level geolocators (GLS) and feather sampling can be similarly effective. METHODS: Here we used GLS to identify wintering areas of northern gannets Morus bassanus and sampled winter grown feathers (confirmed from image analysis of non-breeding birds) to test for spatial gradients in δ13 C and δ15 N in the NE Atlantic. RESULTS: By matching winter-grown feathers with non-breeding location of tracked birds we found latitudinal gradients in δ13 C and δ15 N in neritic waters. Moreover, isotopic patterns were best explained by sea surface temperature. Similar isotope gradients were found in fish muscle sampled at local ports. CONCLUSIONS: Our study reveals the potential of using seabird GLS and feathers to reconstruct large scale isotopic patterns.
Abstract.
Author URL.
McIntosh ALS, Bearhop S, Hilton GM, Shaw JM, Johnson FA (2023). Modelling harvest of Greenland barnacle geese and its implications in mitigating human–wildlife conflict. Journal of Applied Ecology
Cunningham SA, Schafer TLJ, Wikle CK, VonBank JA, Ballard BM, Cao L, Bearhop S, Fox AD, Hilton GM, Walsh AJ, et al (2023). Time-varying effects of local weather on behavior and probability of breeding deferral in two Arctic-nesting goose populations.
Oecologia,
201(2), 369-383.
Abstract:
Time-varying effects of local weather on behavior and probability of breeding deferral in two Arctic-nesting goose populations
Arctic-nesting geese face energetic challenges during spring migration, including ecological barriers and weather conditions (e.g. precipitation and temperature), which in long-lived species can lead to a trade-off to defer reproduction in favor of greater survival. We used GPS location and acceleration data collected from 35 greater white-fronted geese of the North American midcontinent and Greenland populations at spring migration stopovers, and novel applications of Bayesian dynamic linear models to test daily effects of minimum temperature and precipitation on energy expenditure (i.e. overall dynamic body acceleration, ODBA) and proportion of time spent feeding (PTF), then examined the daily and additive importance of ODBA and PTF on probability of breeding deferral using stochastic antecedent models. We expected distinct responses in behavior and probability of breeding deferral between and within populations due to differences in stopover area availability. Time-varying coefficients of weather conditions were variable between ODBA and PTF, and often did not show consistent patterns among birds, indicating plasticity in how individuals respond to conditions. An increase in antecedent ODBA was associated with a slightly increased probability of deferral in midcontinent geese but not Greenland geese. Probability of deferral decreased with increased PTF in both populations. We did not detect any differentially important time periods. These results suggest either that movements and behavior throughout spring migration do not explain breeding deferral or that ecological linkages between bird decisions during spring and subsequent breeding deferral were different between populations and across migration but occurred at different time scales than those we examined.
Abstract.
2022
Woods RD, Swaddle JP, Bearhop S, Colhoun K, Gaze WH, Kay SM, McDonald RA (2022). A Sonic Net deters European starlings<i>Sturnus vulgaris</i>from maize silage stores. Wildlife Society Bulletin, 46(4).
Weegman MD, Walsh AJ, Ogilvie MA, Bearhop S, Hilton GM, Hodgson DJ, Fox AD (2022). Adult survival and per-capita production of young explain dynamics of a long-lived goose population.
IBIS,
164(2), 574-580.
Author URL.
Swan GJF, Bearhop S, Redpath SM, Silk MJ, Padfield D, Goodwin CED, McDonald RA (2022). Associations between abundances of free-roaming gamebirds and common buzzards Buteo buteo are not driven by consumption of gamebirds in the buzzard breeding season.
ECOLOGY AND EVOLUTION,
12(5).
Author URL.
Handby T, Slezacek J, Lupi S, Colhoun K, Harrison XA, Bearhop S (2022). Changes in Behaviour and Proxies of Physiology Suggest Individual Variation in the Building of Migratory Phenotypes in Preparation for Long-Distance Flights. Frontiers in Ecology and Evolution, 10
McIntosh ALS, McIntosh A (2022). Conservation management conflict in the Greenland barnacle goose.
Abstract:
Conservation management conflict in the Greenland barnacle goose
Human population expansion into natural environments has resulted in an increase in human-wildlife conflict. To mitigate these conflicts, numerous management strategies have been implemented worldwide. Several strategies depend on lethal approaches either for population control, or lethal scaring. These impact populations directly through mortality and indirectly through disturbance. Understanding the effect of these strategies is vital to determine their efficacy and ensure the long-term viability of managed populations.
In recent decades, population expansion of several European-wintering goose populations into agricultural areas has resulted in goose-agricultural conflict. This thesis evaluates how shooting management impacts the East Greenland flyway population of Barnacle geese (Branta leucopsis). In chapter two I summarise the effectiveness of scaring for conflict mitigation and identify key factors in maximising success of scaring schemes. Chapter three evaluates the cumulative impact of harvest on flyway-scale population dynamics. I then assess the effect of shooting disturbance on i) foraging site selection (chapter four), ii) movement (chapter five) and iii) foraging behaviour (chapter six). Lastly, I address the cryptic consequences of shooting management including the impact on non-quarry species and the use of lead shot (chapters five and seven).
This review highlights the importance of understanding of species ecology and landscape dynamics when implementing a scaring scheme. Furthermore, scaring is best implemented as a push-pull strategy, balancing scaring at key sites with the provision of suitable refuges for successful redistribution.
Declines in global abundance are associated with increasing harvest rates throughout the flyway. Most notable changes to harvest have occurred on Islay, suggesting that localised Islay-management is the primary cause of flyway decline in abundance.
Finally, I identify refuges as important provisions for effective population management. Refuges are preferentially selected foraging sites in response to direct shooting disturbance, where geese can forage undisturbed. They are also associated with reduced anti-predation behaviour and allow geese to redistribute and recoup energetic losses undisturbed.
As human-wildlife conflict will continue to pose a key conservation issue, effective, evidence-based management strategies will be vital to ensure their efficacy in mitigating conflict and maintaining viable populations. This thesis provides a case study, that assesses the cumulative impact of local shooting on global population dynamics. This can inform future management policies and assist in coordinating international management to prevent overexploitation and highlights important avenues for further research and management.
Abstract.
Goetz KT, Stephenson F, Hoskins A, Bindoff AD, Orben RA, Sagar PM, Torres LG, Kroeger CE, Sztukowski LA, Phillips RA, et al (2022). Data Quality Influences the Predicted Distribution and Habitat of Four Southern-Hemisphere Albatross Species. Frontiers in Marine Science, 9
Bell F (2022). Population declines and carry over effects in sub-Saharan migrant birds.
Abstract:
Population declines and carry over effects in sub-Saharan migrant birds
Across the globe anthropogenic changes are leading to population declines of
migratory bird species. Despite songbirds being one of the most at-risk migratory
groups, understanding of their lifecycle remains limited compared to non-migratory
species, with knowledge of ecology and behaviour outside of the breeding period
and range especially lacking. This thesis initially takes a global perspective to understand the risk of migration as a
strategy. I synthesised population trend data from 94% of extant bird species to
examine whether migratory species are more likely to be in decline than non migrants, and potential geographic and habitat related associations in which
populations are more likely in decline.
Subsequent chapters focus on the migratory European pied flycatcher Ficedula
hypoleuca to explore possible causal mechanisms implicated in population declines
of many Palaearctic-African migratory songbirds. I used a combination of individual based tracking, demographic and investigative methods from two European breeding
populations, and fieldwork in West African non-breeding areas to achieve this.
Our global analysis identifies widespread declines across all taxa, although migratory
bird species are less likely to be in population decline than non-migrants, suggesting
that some migrants may be more robust to the threats of environmental change.
Among migrants, species distributed throughout the year in the northern hemisphere,
within the Palearctic Asian-Australian flyway, or that use savanna habitat are
declining more than other migrants.
In the subsequent chapters, I describe the migratory behaviour of pied flycatchers
across an annual cycle. I find that events and processes experienced during the non breeding season have influence on subsequent breeding timing and success,
mediated by spring stopover behaviour. During potentially costly barrier crossing
flights, the environmental conditions encountered influences migratory plasticity.
Finally, I identify an association between habitat selection in non-breeding areas with
disease prevalence, which may have long-term consequences for population
dynamics.
By identifying the flyways and habitats most associated with migrant decline, the
global analysis has the potential to guide conservation and research priorities.
Through working in both breeding and non-breeding populations of pied flycatchers, I
show that the conditions experienced in the West Africa non-breeding range, and
during spring migration, can influence subsequent reproductive success through
multiple mechanisms.
Our results advance understanding of pied flycatcher non-breeding ecology. These
findings can be generalised to other migratory songbirds, in particular, the influence
of environmental conditions on migratory behaviours.
Abstract.
Newth JL, McDonald RA, Wood KA, Rees EC, Semenov I, Chistyakov A, Mikhaylova G, Bearhop S, Cromie RL, Belousova A, et al (2022). Predicting intention to hunt protected wildlife: a case study of Bewick's swan in the European Russian Arctic.
ORYX,
56(2), 228-240.
Abstract:
Predicting intention to hunt protected wildlife: a case study of Bewick's swan in the European Russian Arctic
Illegal killing of wildlife is a major conservation issue that, to be addressed effectively, requires insight into the drivers of human behaviour. Here we adapt an established socio-psychological model, the theory of planned behaviour, to explore reasons for hunting the Endangered Bewick's swan Cygnus columbianus bewickii in the European Russian Arctic, using responses from hunters to a questionnaire survey. Wider ecological, legal, recreational and economic motivations were also explored. of 236 hunters who participated overall, 14% harboured intentions to hunt Bewick's swan. Behavioural intention was predicted by all components of the theory of planned behaviour, specifically: hunters' attitude towards the behaviour, perceived behavioural control (i.e. perceived capability of being able to perform the behaviour) and their subjective norms (perception of social expectations). The inclusion of attitude towards protective laws and descriptive norm (perception of whether other people perform the behaviour) increased the model's predictive power. Understanding attitudes towards protective laws can help guide the design of conservation measures that reduce non-compliance. We conclude that conservation interventions should target the socio-psychological conditions that influence hunters' attitudes, social norms and perceived behavioural control. These may include activities that build trust, encourage support for conservation, generate social pressure against poaching, use motivations to prompt change and strengthen peoples' confidence to act. This approach could be applied to inform the effective design, prioritization and targeting of interventions that improve compliance and reduce the illegal killing of wildlife.
Abstract.
Mills WF, Ibañez AE, Bustamante P, Carneiro APB, Bearhop S, Cherel Y, Mariano-Jelicich R, McGill RAR, Montalti D, Votier SC, et al (2022). Spatial and sex differences in mercury contamination of skuas in the Southern Ocean.
Environ Pollut,
297Abstract:
Spatial and sex differences in mercury contamination of skuas in the Southern Ocean.
Antarctic marine ecosystems are often considered to be pristine environments, yet wildlife in the polar regions may still be exposed to high levels of environmental contaminants. Here, we measured total mercury (THg) concentrations in blood samples from adult brown skuas Stercorarius antarcticus lonnbergi (n = 82) from three breeding colonies south of the Antarctic Polar Front in the Southern Ocean (southwest Atlantic region): (i) Bahía Esperanza/Hope Bay, Antarctic Peninsula; (ii) Signy Island, South Orkney Islands; and, (iii) Bird Island, South Georgia. Blood THg concentrations increased from the Antarctic Peninsula towards the Antarctic Polar Front, such that Hg contamination was lowest at Bahía Esperanza/Hope Bay (mean ± SD, 0.95 ± 0.45 μg g-1 dw), intermediate at Signy Island (3.42 ± 2.29 μg g-1 dw) and highest at Bird Island (4.47 ± 1.10 μg g-1 dw). Blood THg concentrations also showed a weak positive correlation with δ15N values, likely reflecting the biomagnification process. Males had higher Hg burdens than females, which may reflect deposition of Hg into eggs by females or potentially differences in their trophic ecology. These data provide important insights into intraspecific variation in contamination and the geographic transfer of Hg to seabirds in the Southern Ocean.
Abstract.
Author URL.
Wang X, Bell F, Ouwehand J, Bearhop S, Burgess M, Nicolaus M, Both C (2022). Tracking locally hatched pied flycatchers reveals masking of inherited trait variation during spring migration.
Langley LP, Bearhop S, Burton NHK, Banks AN, Frayling T, Thaxter CB, Clewley GD, Scragg E, Votier SC (2022). Urban and coastal breeding lesser black‐backed gulls (Larus fuscus) segregate by foraging habitat. Ibis, 165(1), 214-230.
Evans SR, Bearhop S (2022). Variation in movement strategies: Capital versus income migration. Journal of Animal Ecology, 91(10), 1961-1974.
Ozsanlav-Harris L, Griffin L, Weegman MD, Cao L, Hilton GM, Bearhop S (2022). Wearable reproductive trackers: quantifying a key life history.
Ozsanlav-Harris L, Griffin LR, Weegman MD, Cao L, Hilton GM, Bearhop S (2022). Wearable reproductive trackers: quantifying a key life history event remotely.
ANIMAL BIOTELEMETRY,
10(1).
Author URL.
Lee SCR, Hodgson DJ, Bearhop S (2022). What has biotelemetry ever done for avian translocations?.
Mov Ecol,
10(1).
Abstract:
What has biotelemetry ever done for avian translocations?
Species translocation is a popular approach in contemporary ecological restoration and rewilding. Improving the efficacy of conservation translocation programmes requires a combination of robust data from comparable populations, population viability modelling and post-release monitoring. Biotelemetry is becoming an ever more accessible means to collect some of the high-resolution information on the ecology and behaviour of founding populations that such evaluations require. Here, we review 81 published case studies to consider how this capability could increase the success of avian translocations. We found that 67 translocations favoured traditional radio telemetry, with surveillance focussing mostly on immediate post-release dispersal, survival and breeding attempts. Just 28 projects tracked founder individuals for longer than 1 year and no studies referenced pre-release sampling or planning using biotelemetry. While our review shows that tracking devices have been deployed extensively in translocation projects, its application has been mostly limited to short-term spatial and demographic monitoring. We conclude that biotelemetry is a powerful tool for harnessing a multitude of lifetime eco-behavioural data which can be used to build valuable predictive models and surveillance programmes, but this capability has yet to be fully realised by researchers in avian translocations.
Abstract.
Author URL.
2021
Brakes P, Carroll EL, Dall SRX, Keith SA, McGregor PK, Mesnick SL, Noad MJ, Rendell L, Robbins MM, Rutz C, et al (2021). A deepening understanding of animal culture suggests lessons for conservation.
Proceedings of the Royal Society B: Biological Sciences,
288(1949).
Abstract:
A deepening understanding of animal culture suggests lessons for conservation
A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.
Abstract.
Cecchetti M, Crowley SL, Goodwin CED, Cole H, McDonald J, Bearhop S, McDonald RA (2021). Contributions of wild and provisioned foods to the diets of domestic cats that depredate wild animals. Ecosphere, 12(9).
Bell O (2021). Ecological effects of Tasmanian devil Sarcophilus harrisii declines.
Abstract:
Ecological effects of Tasmanian devil Sarcophilus harrisii declines
Species declines, which are both widespread and worsening, affect the ecological dynamics not only of declining populations, but also the species with which they interact. In the case of top carnivores, their marked declines are triggering trophic cascades whereby their structuring influence on communities is lost, resulting in release of prey species from predation pressure and sympatric carnivores from competitive pressure. Changes in competitive pressure both within and between sympatric species are predicted to result in changes in the ecological niches of individuals and populations, according to the niche variation hypothesis. Investigating the niche dynamics of communities experiencing top carnivore loss allows us to test theoretical predictions of how ecological niches respond to competition, as well as furthering our understanding of the role and function of top carnivores.
In this thesis, I have explored the effects of Tasmanian devil Sarcophilus harrisii decline, following the emergence of a transmissible cancer, devil facial tumour disease (DFTD). I used stable isotope analysis to characterise the trophic ecology of Tasmanian devils, a top marsupial carnivore, and to investigate the impact of disease and population decline on the trophic niches of devil individuals and populations, and of spotted-tailed quolls Dasyurus maculatus, a closely-related sympatric marsupial carnivore.
I first quantified patterns of isotopic variation within a Tasmanian devil population. Using δ13C and δ15N values from whisker tissue samples collected from Tasmanian devils at Wilmot, Tasmania, I demonstrated that both δ13C and δ15N, and group isotopic niche breadth decreased with increasing age in weaned Tasmanian devils. By characterising the isotopic niche breadth of a subset of individuals, I showed that individual niche breadth also decreased with increasing age, and revealed an isotopic signature of weaning in young Tasmanian devils.
Next, I explored the impact of DFTD on the trophic ecology of infected Tasmanian devils. I tested whether DFTD progression, measured as tumour volume, affected δ13C and δ15N values of whiskers of Tasmanian devils collected at six sites across Tasmania. I found isotope values did not change with increasing tumour volume, except at one site, Freycinet, which showed differences in the relative abundance of three common prey species compared to our other sites, based on species distribution models. I also showed that whisker isotope values of individual Tasmanian devils sampled before and after detection of clinical signs of disease do not differ, when compared to healthy control individuals. I conclude that, according to stable isotope analysis, devils do not generally change their diet in response to DFTD but that contextual ecological factors such as prey availability may elicit or allow a change in diet as the disease progresses.
I then used Bayesian stable isotope mixing models to estimate the proportional contribution of prey groups to the diet of Tasmanian devils. I examined variation in δ13C and δ15N values from Tasmanian devils and their putative prey species at six sites, and concluded only one site was suitable for mixing model analysis. The results suggested that the devil population at Woodbridge, Tasmania, consumed similar amounts of Tasmanian pademelon Thylogale billardierii and small mammals, and fewer Bennett’s wallabies Macropus rufogriseus. I highlight the importance of further research to quantify trophic discrimination factors in marsupial species, and the difficulty in sampling the prey base of opportunistic carnivores, with large ranges relative to their prey.
Considering the potential impact of Tasmanian devil decline on community niche dynamics, I examined the effect of devil decline upon the population and individual-level isotopic niche breadths of both Tasmanian devils and spotted-tailed quolls. The extent of devil decline, using time since disease arrival as a proxy, had no effect on population level isotopic niche breadths. However, niches of both species were significantly smaller in areas with high coverage of human-modified habitat. I did not find evidence of differences in individual specialisation between sites. I conclude that anthropogenic influences on resource availability have a larger impact on carnivore niches in this system than top carnivore decline.
Finally, I conclude by discussing the key findings of this thesis and placing them within the broader contexts of Tasmanian devil ecology, stable isotope analysis and ecological niche variation. This work demonstrates the robustness of Tasmanian devil isotopic niches to disease and decline, and shows that ecological context is a key driver of isotopic variation among Tasmanian devils. This research also reveals some of the challenges and opportunities afforded in applying stable isotope analysis to marsupials, particularly in Australia, which is thus far an under-utilised method in this taxon and in this region of the world. Ultimately, the work of this thesis contributes to our understanding of ecological niche dynamics, and highlights the need to consider both community-level and landscape-level perturbations when investigating ecological niches in changing communities.
Abstract.
Langley LP, Bearhop S, Burton NHK, Banks AN, Frayling T, Thaxter CB, Clewley GD, Scragg E, Votier SC (2021). GPS tracking reveals landfill closures induce higher foraging effort and habitat switching in gulls.
MOVEMENT ECOLOGY,
9(1).
Author URL.
Bell F, Bearhop S, Briedis M, El Harouchi M, Bell SC, Castello J, Burgess M (2021). Geolocators reveal variation and sex‐specific differences in the migratory strategies of a long‐distance migrant. Ibis, 164(2), 451-467.
Bell O, Jones ME, Cunningham CX, Ruiz-Aravena M, Hamilton DG, Comte S, Hamede RK, Bearhop S, McDonald RA (2021). Isotopic niche variation in Tasmanian devils Sarcophilus harrisii with progression of devil facial tumor disease.
Ecology and Evolution,
11(12), 8038-8053.
Abstract:
Isotopic niche variation in Tasmanian devils Sarcophilus harrisii with progression of devil facial tumor disease
Devil facial tumor disease (DFTD) is a transmissible cancer affecting Tasmanian devils Sarcophilus harrisii. The disease has caused severe population declines and is associated with demographic and behavioral changes, including earlier breeding, younger age structures, and reduced dispersal and social interactions. Devils are generally solitary, but social encounters are commonplace when feeding upon large carcasses. DFTD tumors can disfigure the jaw and mouth and so diseased individuals might alter their diets to enable ingestion of alternative foods, to avoid conspecific interactions, or to reduce competition. Using stable isotope analysis (δ13C and δ15N) of whiskers, we tested whether DFTD progression, measured as tumor volume, affected the isotope ratios and isotopic niches of 94 infected Tasmanian devils from six sites in Tasmania, comprising four eucalypt plantations, an area of smallholdings and a national park. Then, using tissue from 10 devils sampled before and after detection of tumors and 8 devils where no tumors were detected, we examined whether mean and standard deviation of δ13C and δ15N of the same individuals changed between healthy and diseased states. δ13C and δ15N values were generally not related to tumor volume in infected devils, though at one site, Freycinet National Park, δ15N values increased significantly as tumor volume increased. Infection with DFTD was not associated with significant changes in the mean or standard deviation of δ13C and δ15N values in individual devils sampled before and after detection of tumors. Our analysis suggests that devils tend to maintain their isotopic niche in the face of DFTD infection and progression, except where ecological conditions facilitate a shift in diets and feeding behaviors, demonstrating that ecological context, alongside disease severity, can modulate the behavioral responses of Tasmanian devils to DFTD.
Abstract.
Gimenez J, Arneill GE, Bennison A, Pirotta E, Gerritsen HD, Bodey TW, Bearhop S, Hamer KC, Votier S, Jessopp M, et al (2021). Sexual Mismatch Between Vessel-Associated Foraging and Discard Consumption in a Marine Top Predator.
FRONTIERS IN MARINE SCIENCE,
8 Author URL.
Clark BL, Cox SL, Atkins KM, Bearhop S, Bicknell AWJ, Bodey TW, Cleasby IR, Grecian WJ, Hamer KC, Loveday BR, et al (2021). Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable.
Marine Ecology Progress Series,
661, 1-16.
Abstract:
Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable
Sex-specific niche differentiation is common in marine vertebrates, but how this varies long-term is poorly understood. Here we investigated interannual variation in sexual segregation among breeding northern gannets Morus bassanus, wide-ranging central-place foragers with slight sexual dimorphism. Over 11 breeding seasons, we used GPS tracking and/or stable isotopes to test for sex differences in foraging trip characteristics (range, duration and timing); spatial distribution; habitat selection; and carbon and nitrogen isotopes in blood. When combining data from all years, females foraged further and for longer than males, yet despite this, the foraging areas of the sexes almost completely overlapped. Males and females selected foraging habitats that differed in terms of oceanography but not fishing vessel density. We also detected temporal segregation: females were more likely to be at sea during the day than at night, while males were more likely to be at sea during the night. However, foraging behaviour quantified by all GPS analyses varied interannually, with sex differences detected in some years but not others. Finally, males had consistently higher red blood cell δ13C and δ15N than females across all years, which was not driven by size dimorphism, instead likely by prey choice or very fine-scale habitat selection. We conclude that environmental variation influenced short-term sex differences in movement, but sex differences in stable isotopes that integrate behaviour over longer periods reveal more consistent differences. Our results suggest that inferences drawn from single-year studies may not relate to general patterns, highlighting the importance of long-term studies and combining methods.
Abstract.
Doyle S, Cabot D, Griffin L, Kane A, Colhoun K, Bearhop S, McMahon BJ (2021). Spring and autumn movements of an Arctic bird in relation to temperature and primary production.
JOURNAL OF AVIAN BIOLOGY,
52(11).
Author URL.
Langley L (2021). The ecology of lesser black-backed gulls (Larus fuscus) in the Anthropocene: implications for conservation and management.
Abstract:
The ecology of lesser black-backed gulls (Larus fuscus) in the Anthropocene: implications for conservation and management
Context:
Anthropogenic change is affecting many species, with both positive and negative impacts. Human habitat modification and resource subsidies have helped opportunistic species, leading to demographic expansions. However, anthropogenic changes may also harm these opportunists or present future risks, for instance, dependence on subsidies or increased human wildlife interactions. Understanding human influences on these opportunistic species’ ecology is essential for their effective conservation and management in a changing world.
Approaches:
Using gulls (Laridae) as a model, this thesis first summarises global trends in their abundance and distribution, the drivers of these changes and the challenges for their conservation and management. The three subsequent chapters examine how human activities have influenced the ecology of lesser black-backed gulls (Larus fuscus) in northwest England, combining telemetry data, and field sampling and monitoring. First, I investigate changes to gulls’ foraging ecology and adult body condition after landfill closures. Second, I investigate population-level differences in movement and breeding ecology between neighbouring urban and coastal colonies. Finally, I examine the degree of individual foraging site fidelity both within and among colonies.
Results:
First, the review highlighted anthropogenic change as a key driver of demographic expansions in gull populations; however, there were geographic biases in the literature and evidence of recent declines suggest ecological processes linking humans and gulls are complex, necessitating care when making decisions about gull conservation and management. Second, telemetry data revealed strong behavioural responses to anthropogenic perturbations, with increased foraging effort and habitat-switching observed following landfill closures. Third, I found evidence for foraging habitat segregation between urban and rural lesser black-backed gulls. However, this did not results in major differences in diet or breeding performance between colonies. Finally, I found a high degree of individual variation in foraging site fidelity, with populations composed of a mixture of site faithful and varied individuals.
Implications:
The review highlights the urgent need to quantify the efficacy of management approaches in mitigating gull impacts and conservation measures in arresting gull declines. The observation of spatial segregation between breeding habitats demonstrates clear differences in foraging ecology between colonies, and highlights measures targeting urban foragers as a useful tool for mitigating human-gull interactions and the need for conservation action, such as the restoration of coastal ecosystems, to boost declining coastal colonies. Additionally, the finding of habitat-switching following landfill closures suggests anthropogenic perturbations will alter the distribution of foraging gulls and increase the incidence of human-gull interactions and possibly conflict. However, we found that site fidelity, use of urban habitats and responses to landfill closures varied among years, colonies, and individual gulls. This demonstrates the need for long-term monitoring of ecological and demographic responses to human activities across a range of colonies. This will provide the requisite ecological evidence to develop landscape-scale management plans for opportunistic species such as gulls, which balance mitigation of negative impacts with conservation.
Abstract.
Mills B (2021). Trophic Ecology and Mercury Contamination of Seabird Communities in the Southern Ocean.
Abstract:
Trophic Ecology and Mercury Contamination of Seabird Communities in the Southern Ocean
This thesis examines inter- and intraspecific variation in the trophic ecology and mercury (Hg) contamination of seabirds in the Southern Ocean, with a focus on the seabird community at Bird Island, South Georgia. In the opening chapter, I outline the key themes of the thesis, including the various methods of studying seabird diets and drivers of Hg burdens. Next, in Chapter 2, I analyse variation in the diets of black-browed albatrosses Thalassarche melanophris and grey-headed albatrosses T. chrysostoma since the mid-1990s. This study revealed long-term dietary shifts in both species, which were partly related to proxies of prey availability and had repercussions for breeding success in grey-headed albatrosses. Chapter 3 is the first conventional diet study of northern giant petrels Macronectes halli and southern giant petrels M. giganteus for >35 years at South Georgia. Penguins were the most important prey, and although I found no interspecific differences in overall diet composition, there was variation between sexes, by month and among years. In Chapter 4, using stable isotope ratios of carbon and nitrogen in feathers, I demonstrate a high degree of intraspecific variation in the trophic ecology of grey-headed albatrosses during the non-breeding period. I then analysed Hg contamination in their feathers (Chapter 5), which were the highest recorded in the genus and showed a threefold increase over the past 25 years. Hg concentrations were much lower in feathers moulted in Antarctic than sub-Antarctic waters, and contamination also increased with trophic level. Importantly, Hg burdens were higher in failed than successful males. In Chapter 6, I analysed Hg in blood of brown skuas Stercorarius antarcticus lonnbergi from three breeding populations, revealing geographic differences in the transfer of Hg to skuas in the Southern Ocean, sex differences in contamination levels and relationships with trophic ecology. The final chapter summarises the main findings of the thesis and highlights how emerging techniques may enhance future research on foraging ecology and pollutants.
Abstract.
Lemos Gonçalves GR, Melo dos Santos PV, Costa VE, Negreiros-Fransozo ML, Bearhop S, Castilho AL (2021). Trophic relationships between the crab Libinia ferreirae and its symbionts. Marine Environmental Research, 171, 105479-105479.
2020
Bell O, Jones ME, Ruiz‐Aravena M, Hamede RK, Bearhop S, McDonald RA (2020). Age‐related variation in the trophic characteristics of a marsupial carnivore, the Tasmanian devil. <i>Sarcophilus harrisii</i>. Ecology and Evolution, 10(14), 7861-7871.
Bodey TW, Cleasby IR, Blount JD, McElwaine G, Vigfusdottir F, Bearhop S (2020). Consistent measures of oxidative balance predict survival but not reproduction in a long-distance migrant.
J Anim Ecol,
89(8), 1872-1882.
Abstract:
Consistent measures of oxidative balance predict survival but not reproduction in a long-distance migrant.
Physiological processes, including those that disrupt oxidative balance, have been proposed as key to understanding fundamental life-history trade-offs. Yet, examination of changes in oxidative balance within wild animals across time, space and major life-history challenges remains uncommon. For example, migration presents substantial physiological challenges for individuals, and data on migratory individuals would provide crucial context for exposing the importance of relationships between oxidative balance and fitness outcomes. Here we examined the consistency of commonly used measures of oxidative balance in longitudinally sampled free-living individuals of a long-lived, long-distance migrant, the Brent goose Branta bernicla hrota over periods of months to years. Although inter-individual and temporal variation in measures of oxidative balance were substantial, we found high consistency in measures of lipid peroxidation and circulating non-enzymatic antioxidants in longitudinally sampled individuals. This suggests the potential for the existence of individual oxidative phenotypes. Given intra-individual consistency, we then examined how these physiological measures relate to survival and reproductive success across all sampled individuals. Surprisingly, lower survival was predicted for individuals with lower levels of damage, with no measured physiological metric associated with reproductive success. Our results demonstrate that snapshot measurements of a consistent measure of oxidative balance can inform our understanding of differences in a key demographic trait. However, the positive relationship between oxidative damage and survival emphasises the need to investigate the relationships between the oxidative system and fitness outcomes in other species undergoing similar physiologically challenging life cycles. This would highlight the extent to which variation in such traits and resource allocation trade-offs is a result of adaptation to different life-history strategies.
Abstract.
Author URL.
Parr N (2020). Flights Across the Roof of the World.
Abstract:
Flights Across the Roof of the World
High-altitude environments present challenges to animal life, including cold temperatures, dehydration and reduced barometric pressure, resulting in diminished oxygen availability (hypoxia). Birds that migrate across high-altitude mountain ranges face these challenges whilst meeting the high metabolic demands of flight. In this thesis I develop scientific understanding of how avian migrants overcome this challenge and cross the Tibetan Plateau (the highest and largest land mass on Earth). Firstly, I consolidate research into the benefits that avian physiology can confer for funding high rates of metabolism at high altitude, relative to humans and other mammals. Secondly, I present empirical work that aims to investigate high-altitude flight during migration across the Tibetan Plateau, expanding the scientific literature that has previously focused on bar-headed geese (Anser indicus). I collate tracking data for nine species of birds that migrate across or around the Himalayas and Tibetan Plateau and investigate whether there are common techniques that reduce flight costs and minimise exposure to hypoxia. I also explore how thermoregulation in bar-headed geese may be affected by high altitude, using high resolution data collected during free flight over the Tibetan Plateau. Finally, I compare the muscular phenotype of high-altitude migrant ruddy shelduck (Tadorna ferruginea) and low-altitude congener, common shelduck (Tadorna tadorna), to investigate whether ruddy shelduck have physiological adaptations for flight at high altitude. The research carried out in this thesis reveals that i) multiple species reach altitudes in excess of 6,000 m whilst crossing the Tibetan Plateau, including cranes, raptors and waterfowl who’s flight altitudes have not been previously quantified; ii) with the exception of demoiselle cranes, most bird species reduce altitude exposure where possible; iii) bar-headed geese maintain core body temperatures within a relatively narrow range regardless of altitude, expanding our understanding of the high-altitude physiology of this iconic species; iv) ruddy shelduck may have adaptations to enhance the functional properties of mitochondrial enzymes, which may support high-altitude flight. Collectively, this work advances our knowledge of how migrants overcome the challenge of migration across high altitude through both physiological and behavioural adaptation and adjustment.
Abstract.
Newth J (2020). Lead Poisoning and Illegal Hunting of. Migratory Swans: from biological effects to conservation conflict.
Abstract:
Lead Poisoning and Illegal Hunting of. Migratory Swans: from biological effects to conservation conflict
Conflicts between people over protecting biodiversity are ubiquitous, damaging and among the most challenging problems facing wildlife conservation worldwide. Such conflicts typically emerge from ‘biodiversity impacts’ when there are disagreements about the management and allocation of natural resources. They are characterised by their inherent multi-layered complexity and their negative impacts on biodiversity, livelihoods and human wellbeing. A shift towards a greater understanding of the human causal drivers of complex conservation issues as well as their ecological impacts is urgently needed to prevent and de-escalate conflicts and halt potentially catastrophic biodiversity loss. I explore the ecological and socio-psychological contexts of two complex conservation issues – the illegal killing of Bewick’s swans Cygnus columbianus bewickii in the Russian Arctic (regarded as a biodiversity impact at risk of emerging as a conflict) and the poisoning of waterbirds from lead ammunition in the UK (currently in a ‘destructive’ phase of conflict) – using approaches and methodologies from the natural and social sciences and psychology. I also provide novel insights into their management and wildlife management more broadly.
I first examine the lesser known impacts of blood lead levels on the physiology of wild birds. I determine that sub-lethal impacts of lead on the body condition of Icelandic-breeding whooper swans Cygnus cygnus occur at the lower end of previously established clinical thresholds. Despite partial restrictions on the use of lead ammunition in the UK, I found a high prevalence of lead poisoning within this swan population. I recommend that previously suggested thresholds for adverse clinical effects should be revised downwards for free-living wildfowl. These findings reaffirm the importance of reducing contamination of the environment with lead shot and thus the availability and exposure of lead to waterbirds.
Next, using Q-methodology, I examined the perspectives of ammunition users around the use of lead ammunition and its potential impacts on wildlife and humans. Disagreements on the risks arising from the use of lead ammunition and appropriate mitigation measures continue to strain relationships between conservation and shooting stakeholder groups in the UK. I identified two statistically and qualitatively distinct perspectives (‘Open to change’ and ‘Status quo’) among ammunition users, and areas of consensus between these. I argue that the clarification of views held presents an opportunity for the shooting community and other stakeholders to take forward discussions and potentially forge new solutions for this long-running conflict.
To identify effective management approaches for reducing the illegal hunting of Bewick’s swans in the Russian Arctic, I examined the risk of accidental hunting and the drivers of deliberate hunting using responses to a questionnaire survey. I found an overall inability of hunters to visually distinguish between three swan species and conclude that the risk of Bewick’s swans being hunted arises in part when they are mistaken for the whooper and mute swan Cygnus olor, both of which are afforded weaker legal protections than the Bewick’s swan in certain areas. Additionally, a significant proportion of hunters were ignorant of the protective laws. I therefore recommend technical solutions that inform hunters about species identification and protective laws. The clarification and mitigation of this issue at the earliest opportunity will help prevent it from emerging as an intractable conservation conflict between conservationists and resource users.
Next, using the Theory of Planned Behaviour, I assessed the drivers for deliberate hunting. Hunters were more likely to harbour hunting intentions if they held negative attitudes towards protective laws and positive or neutral attitudes towards hunting Bewick’s swans, perceived few or no practical barriers to hunting them, and believed that the behaviour was socially acceptable. Wider ecological, recreation, legal and economic motivations were also identified. Future conservation interventions should therefore target social and psychological conditions that influence hunters’ attitudes, social norms and perceived behavioural control.
Finally, I collate the findings of this thesis and use an established conflict typology to partition the varying dimensions and thematic features of the lead shot conflict and identify characteristics of the illegal hunting issue that may facilitate its emergence as a conservation conflict. I suggest that conflict management approaches can be applied to complex biodiversity impacts to prevent their transition to conflict.
Abstract.
Mills WF, Xavier JC, Bearhop S, Cherel Y, Votier SC, Waluda CM, Phillips RA (2020). Long-term trends in albatross diets in relation to prey availability and breeding success. Marine Biology, 167(3).
Mills WF, Bustamante P, McGill RAR, Anderson ORJ, Bearhop S, Cherel Y, Votier SC, Phillips RA (2020). Mercury exposure in an endangered seabird: long-term changes and relationships with trophic ecology and breeding success.
Proceedings of the Royal Society B: Biological Sciences,
287(1941), 20202683-20202683.
Abstract:
Mercury exposure in an endangered seabird: long-term changes and relationships with trophic ecology and breeding success
. Mercury (Hg) is an environmental contaminant which, at high concentrations, can negatively influence avian physiology and demography. Albatrosses (Diomedeidae) have higher Hg burdens than all other avian families. Here, we measure total Hg (THg) concentrations of body feathers from adult grey-headed albatrosses (
. Thalassarche chrysostoma
. ) at South Georgia. Specifically, we (i) analyse temporal trends at South Georgia (1989–2013) and make comparisons with other breeding populations; (ii) identify factors driving variation in THg concentrations and (iii) examine relationships with breeding success. Mean ± s.d. feather THg concentrations were 13.0 ± 8.0 µg g
. −1
. dw, which represents a threefold increase over the past 25 years at South Georgia and is the highest recorded in the
. Thalassarche
. genus. Foraging habitat, inferred from stable isotope ratios of carbon (
. δ
. 13
. C), significantly influenced THg concentrations—feathers moulted in Antarctic waters had far lower THg concentrations than those moulted in subantarctic or subtropical waters. THg concentrations also increased with trophic level (
. δ
. 15
. N), reflecting the biomagnification process. There was limited support for the influence of sex, age and previous breeding outcome on feather THg concentrations. However, in males, Hg exposure was correlated with breeding outcome—failed birds had significantly higher feather THg concentrations than successful birds. These results provide key insights into the drivers and consequences of Hg exposure in this globally important albatross population.
.
Abstract.
Soriano-Redondo A, Gutiérrez JS, Hodgson D, Bearhop S (2020). Migrant birds and mammals live faster than residents.
Nature Communications,
11(1).
Abstract:
Migrant birds and mammals live faster than residents
AbstractBillions of vertebrates migrate to and from their breeding grounds annually, exhibiting astonishing feats of endurance. Many such movements are energetically costly yet there is little consensus on whether or how such costs might influence schedules of survival and reproduction in migratory animals. Here we provide a global analysis of associations between migratory behaviour and vertebrate life histories. After controlling for latitudinal and evolutionary patterns, we find that migratory birds and mammals have faster paces of life than their non-migratory relatives. Among swimming and walking species, migrants tend to have larger body size, while among flying species, migrants are smaller. We discuss whether pace of life is a determinant, consequence, or adaptive outcome, of migration. Our findings have important implications for the understanding of the migratory phenomenon and will help predict the responses of bird and mammal species to environmental change.
Abstract.
Bodey TW, Barnett R, Feu CR, Clark JR, Bearhop S (2020). Nesting outcomes under anthropogenic change – effects of changing climate and nestbox provision on the reproduction of Great Tits. <i>Parus major</i>. Ibis, 163(1), 65-78.
McNicol CM, Bavin D, Bearhop S, Bridges J, Croose E, Gill R, Goodwin CED, Lewis J, MacPherson J, Padfield D, et al (2020). Postrelease movement and habitat selection of translocated pine martens Martes martes.
ECOLOGY AND EVOLUTION,
10(11), 5106-5118.
Author URL.
Doyle S, Cabot D, Walsh A, Inger R, Bearhop S, McMahon BJ (2020). Temperature and precipitation at migratory grounds influence demographic trends of an Arctic-breeding bird.
Glob Chang Biol,
26(10), 5447-5458.
Abstract:
Temperature and precipitation at migratory grounds influence demographic trends of an Arctic-breeding bird.
Anthropogenic climate disruption, including temperature and precipitation regime shifts, has been linked to animal population declines since the mid-20th century. However, some species, such as Arctic-breeding geese, have thrived during this period. An increased understanding of how climate disruption might link to demographic rates in thriving species is an important perspective in quantifying the impact of anthropogenic climate disruption on the global state of nature. The Greenland barnacle goose (Branta leucopsis) population has increased tenfold in abundance since the mid-20th century. A concurrent weather regime shift towards warmer, wetter conditions occurred throughout its range in Greenland (breeding), Ireland and Scotland (wintering) and Iceland (spring and autumn staging). The aim of this study was to determine the relationship between weather and demographic rates of Greenland barnacle geese to discern the role of climate shifts in the population trend. We quantified the relationship between temperature and precipitation and Greenland barnacle goose survival and productivity over a 50 year period from 1968 to 2018. We detected significant positive relationships between warmer, wetter conditions on the Icelandic spring staging grounds and survival. We also detected contrasting relationships between warmer, wetter conditions during autumn staging and survival and productivity, with warm, dry conditions being the most favourable for productivity. Survival increased in the latter part of the study period, supporting the possibility that spring weather regime shifts contributed to the increasing population trend. This may be related to improved forage resources, as warming air temperatures have been shown to improve survival rates in several other Arctic and northern terrestrial herbivorous species through indirect bottom-up effects on forage availability.
Abstract.
Author URL.
Marsh LE (2020). The urban Herring gull, foraging niche and interactions with humans.
Abstract:
The urban Herring gull, foraging niche and interactions with humans
Gulls (Laridae) are of significant interest because of their use and breeding in urban environments, which has increased human-wildlife conflicts. However, there is a lack of information that summarises population trends in gulls, that is driving them towards conflicts with humans; the attitude towards gulls that the public has, especially in urban environments and the factors that determine those attitudes; and how gulls utilise the urban environment for reproductive success.
In this thesis, I explore the literature around gull trends throughout the Western Hemisphere. Using a questionnaire, I attempt to collate information about the public’s attitude towards gulls, paired with spatial correlation to demonstrate geographic differences. I also use gull pellets and foraging effort to explore the niche of gulls, and test for differences between urban and rural birds. The findings show gull population changes are constant, and that public attitude is negative towards gulls, with age and knowledge about gulls effecting negative perceptions. I also demonstrate that rural and urban gulls have differing habitat use periodically through the breeding season but have commonality in foraging effort.
Abstract.
McNicol CM, Bavin D, Bearhop S, Ferryman M, Gill R, Goodwin CED, MacPherson J, Silk MJ, McDonald RA (2020). Translocated native pine martens. <i>Martes martes</i>. alter short‐term space use by invasive non‐native grey squirrels. <i>Sciurus carolinensis</i>. Journal of Applied Ecology, 57(5), 903-913.
2019
Brakes P, Dall SRX, Aplin LM, Bearhop S, Carroll EL, Ciucci P, Fishlock V, Ford JKB, Garland EC, Keith SA, et al (2019). Animal cultures matter for conservation. Science
Newth JL, Wood KA, McDonald RA, Nuno A, Semenov I, Chistyakov A, Mikhaylova G, Bearhop S, Belousova A, Glazov P, et al (2019). Conservation implications of misidentification and killing of protected species. Conservation Science and Practice, 1(5), e24-e24.
McNicol CM (2019). Ecology of translocated pine martens Martes martes and their impacts on grey squirrels Sciurus carolinensis.
Abstract:
Ecology of translocated pine martens Martes martes and their impacts on grey squirrels Sciurus carolinensis
The rate of biodiversity loss has been increasing since the beginning of the Anthropocene, driven by climate change, human population expansion and environmental degradation. Consequently, ecosystems have become simplified through the loss of important processes and species. Ecological restoration aims to reverse such changes through reinstating habitats, native species and their associated relationships, as well as removing invasive, non-native species. One strategy to restore ecological function is through the re-establishment of top-down processes driven by predators. The cascading effects of these predators, through direct predation and the fear they induce in prey can restore predator-prey dynamics in a disrupted food web.
In this thesis, I investigate the restoration of a native and recovering predator, the pine marten Martes martes, with particular focus on its ecology and behaviour after a translocation event from Scotland to Wales. Subsequently, I assess its impact on the behaviour of one of its prey species, the invasive, non-native grey squirrel Sciurus carolinensis to better understand the relationship between these two species.
I first introduce predator restoration using translocation in a project that aims to reintroduce and restore the native pine marten. I demonstrate that the phases of post-translocation movement comprise a period of ‘exploration’ followed by ‘settlement’ in all individuals, however the extent and duration of these movements differ between release groups. I show that conspecific presence is important in site fidelity and the resulting habitat in which martens establish themselves. I then investigate the diet of translocated martens at a population and individual level, before and after translocation. I reveal that pine martens consume a more diverse diet post-translocation, which incorporates grey squirrels, a prey item not found in their source sites in Scotland. Furthermore I document a degree of dietary specialisation within individuals, which is maintained relative to others after translocation. This suggests pine martens are facultative specialists with dietary preferences that they are able to supplement with readily available prey groups, enhancing their probability of survival after translocation.
Next, I address the impact of translocated pine martens on grey squirrel space use and survival. Grey squirrel range size and daily distance travelled was found to increase with increasing marten exposure. However, an impact on grey squirrel survival and range location was not found within the timeframe of this study. I then investigated the role that fear plays in the relationship between pine martens and grey squirrels. Using feeding experiments, I document a reduced volume of food consumed by squirrels in woodlands containing pine martens, suggesting that squirrels ‘give-up’ foraging earlier under such conditions. This suggests that squirrels display a fear-mediated response to pine marten risk, which in time may be detrimental to grey squirrel fitness. I consider the role of predation and fear in predator-prey dynamics and its importance in species management.
Finally I conclude the key findings of this thesis with regards to pine marten and grey squirrel management in the UK, as well as their contribution to carnivore restoration and species management strategies. This work identifies that social structure and dietary flexibility are key considerations for predator restoration projects. Furthermore, the cascading effects of predators can play a potential role in the management of invasive non-native species, which may be more economically and socially acceptable than current strategies. This work highlights the importance of studying ecological processes underlying landscape-scale patterns to better inform the management of native and non-native species alike.
Abstract.
Swan GJF, Bearhop S, Redpath SM, Silk MJ, Goodwin CED, Inger R, McDonald RA (2019). Evaluating Bayesian stable isotope mixing models of wild animal diet and the effects of trophic discrimination factors and informative priors. Methods in Ecology and Evolution, 11(1), 139-149.
Grecian WJ, Williams HJ, Votier SC, Bearhop S, Cleasby IR, Gremillet D, Hamer KC, Le Nuz M, Lescroel A, Newton J, et al (2019). Individual Spatial Consistency and Dietary Flexibility in the Migratory Behavior of Northern Gannets Wintering in the Northeast Atlantic.
FRONTIERS IN ECOLOGY AND EVOLUTION,
7 Author URL.
Bearhop S, Bodey T, Cleasby IR, Blount J, Vigfusdottir F, MacKie K (2019). Measures of oxidative state are primarily driven by extrinsic factors in a long-distance migrant. Biology Letters, 15, 1-4.
Deakin Z, Hamer KC, Sherley RB, Bearhop S, Bodey TW, Clark BL, James Grecian W, Gummery M, Lane J, Morgan G, et al (2019). Sex differences in migration and demography of a wide-ranging seabird, the Northern Gannet.
Marine Ecology Progress Series,
622, 191-201.
Abstract:
Sex differences in migration and demography of a wide-ranging seabird, the Northern Gannet
Marine vertebrates show a diversity of migration strategies, including sex differences. This may lead to differential demography, but the consequences of such between-sex variation are little understood. Here, we studied the migration of known-sex northern gannets Morus bassanus — a partial migrant with females ~8 % heavier than males. We used geolocators to determine wintering areas of 49 breeding adults (19 females and 30 males during 2010 to 2014) from 2 colonies in the northeast Atlantic (Bass Rock and Grassholm, UK). We also tested for sex-specific survival probabilities using capture−mark−recapture methods (n = 72 individuals Bass Rock, n = 229 individuals Grassholm; 2010−2018) and applied sex-specific population projection matrices (PPMs) to quantify population-level effects. Tracked gannets wintered in a range of large marine ecosystems (LMEs): Canary Current LME (CCLME; 69 %), Celtic-Biscay Shelf LME (16 %), Iberian Coastal LME (8 %), North Sea LME (4 %) or Mediterranean LME (2 %). Migratory destination differed between the sexes: 90 % of females vs. 57 % of males wintered in the CCLME. Survival was similar between the sexes at Bass Rock (mean ± 95 % CI = 0.951 ± 0.053 and 0.956 ± 0.047 for females and males, respectively). At Grassholm, there was evidence of slight sex differences in breeder survival: females had lower annual survival (0.882 ± 0.040) than males (0.946 ± 0.026). At Bass Rock, PPMs with no sex effect best fitted the observed population increase (1994−2014). Sex-specific PPMs fitted the population estimates for Grassholm (1995−2015). Our results reveal that female gannets are more likely to travel further than males to winter in the CCLME. This difference is unlikely due to morphological differences, unlike in other bird species. However, the reason for slightly higher over-winter female mortality at Grassholm is unclear.
Abstract.
Mills L (2019). Testing agricultural impacts on breeding ground food resources as a driver of cuckoo population decline.
Abstract:
Testing agricultural impacts on breeding ground food resources as a driver of cuckoo population decline
The common cuckoo Cuculus canorus has undergone a striking divergence in population trend between UK habitats since the 1980s. The breeding population in Scotland – in largely semi-natural open habitat – shows significant increase whereas there has been a significant decline in England. Here breeding numbers have remained stable or increased in semi-natural habitats, while woodland and farmland populations have plummeted. As a brood parasitic bird with a long-distance annual migration, the cuckoo has a unique network of relationships to songbird ‘hosts’, prey and habitat; and a disconnection between adult and nestling ecology due to lack of parental care. This thesis investigated the role of breeding ground land-use factors in driving cuckoo population decline. In the first chapter information was synthesised from the literature on potential threats and environmental impacts facing cuckoo populations, which also highlighted knowledge gaps and a basis for hypotheses in later chapters. In chapters 3 and 4 I investigated land-use and habitat influences on the nestling ecology of the cuckoo and a key host the meadow pipit Anthus pratensis at field sites in Dartmoor, Devon, UK. I assessed provisioning behaviour at unparasitised nests of meadow pipit, and used this baseline to test how host provisioning differed between host broods and cuckoo nestlings and fledglings, as indicators of how resource requirements differ between cuckoo and host in a relative stronghold habitat. There was evidence that host foraging habitat selection and investment in provisioning per unit time were similar between raising a cuckoo nestling and a host brood; but the nestling and fledgling periods were longer in cuckoos and the rate of provisioning was higher for cuckoo fledglings. Pipits also provided cuckoos with different diversity and frequency of prey taxa, further indicating that cuckoo nesting success requires different resources to that of unparasitised nests. In chapters 5 and 6 I focused on the diet of adult and juvenile cuckoos. In the first application of DNA sequencing to the study of cuckoo diet, adults in a relative stronghold habitat consumed large moth caterpillars (Lepidoptera) but frequently consumed Orthoptera and some Diptera families not previously reported as important prey. Analysis of moth capture data in Devon suggested some key prey species have declined even in semi-natural upland areas. I conclude with analysis of key findings including how they direct future research and conservation.
Abstract.
Soriano-Redondo A, Hilton GM, Gutiérrez JS, Lock L, Stanbury A, Votier SC, Bearhop S (2019). The role of immigration and reinforcement in the population dynamics of a long-lived bird: implications for the conservation of threatened species.
Animal Conservation,
22(1), 49-58.
Abstract:
The role of immigration and reinforcement in the population dynamics of a long-lived bird: implications for the conservation of threatened species
Understanding population dynamics requires knowledge of the differential effects of survival, productivity and dispersal on population growth. This is particularly important for the conservation of small and recently established populations, where stochastic births and deaths may result in negative growth and even extinction. Here, we investigated the population dynamics of a small population of Eurasian cranes Grus grus in the UK and the effect of a population reinforcement in population growth. We also estimated the probability that the conservation status of cranes improves in the future. We developed stochastic population models to assess the population dynamics and the effect of adding 90 individuals between 2010 and 2014. The best-supported models suggest that the crane population is self-sustaining with an annual adult survival of 0.88, but suffers from low productivity. In addition, much of the population increase has been driven by immigration of birds from continental Europe. We found that population reinforcement resulted in a 50% increase in the projected population size, from 178 to 275 breeding pairs over the next 50 years. We showed that the relative contribution of immigration to population growth declined from 43%, when the translocated birds were not considered, to 29%, when they were included in the breeding pool. Moreover, after the population reinforcement, the probability of the population improving its conservation status increased from just above zero to 32%. In light of the recent increase in translocation programs worldwide, our study highlights the need to consider population dynamics to successfully predict the increase in population size when management strategies, such as reintroductions and reinforcements, are planned.
Abstract.
Soriano-Redondo A, Jones-Todd CM, Bearhop S, Hilton GM, Lock L, Stanbury A, Votier SC, Illian JB (2019). Understanding species distribution in dynamic populations: a new approach using spatio-temporal point process models.
Ecography,
42(6), 1092-1102.
Abstract:
Understanding species distribution in dynamic populations: a new approach using spatio-temporal point process models
Understanding and predicting a species’ distribution across a landscape is of central importance in ecology, biogeography and conservation biology. However, it presents daunting challenges when populations are highly dynamic (i.e. increasing or decreasing their ranges), particularly for small populations where information about ecology and life history traits is lacking. Currently, many modelling approaches fail to distinguish whether a site is unoccupied because the available habitat is unsuitable or because a species expanding its range has not arrived at the site yet. As a result, habitat that is indeed suitable may appear unsuitable. To overcome some of these limitations, we use a statistical modelling approach based on spatio-temporal log-Gaussian Cox processes. These model the spatial distribution of the species across available habitat and how this distribution changes over time, relative to covariates. In addition, the model explicitly accounts for spatio-temporal dynamics that are unaccounted for by covariates through a spatio-temporal stochastic process. We illustrate the approach by predicting the distribution of a recently established population of Eurasian cranes Grus grus in England, UK, and estimate the effect of a reintroduction in the range expansion of the population. Our models show that wetland extent and perimeter-to-area ratio have a positive and negative effect, respectively, in crane colonisation probability. Moreover, we find that cranes are more likely to colonise areas near already occupied wetlands and that the colonisation process is progressing at a low rate. Finally, the reintroduction of cranes in SW England can be considered a human-assisted long-distance dispersal event that has increased the dispersal potential of the species along a longitudinal axis in S England. Spatio-temporal log-Gaussian Cox process models offer an excellent opportunity for the study of species where information on life history traits is lacking, since these are represented through the spatio-temporal dynamics reflected in the model.
Abstract.
Cleasby IR, Wakefield ED, Morrissey BJ, Bodey TW, Votier SC, Bearhop S, Hamer KC (2019). Using time-series similarity measures to compare animal movement trajectories in ecology.
Behavioral Ecology and Sociobiology,
73(11).
Abstract:
Using time-series similarity measures to compare animal movement trajectories in ecology
Abstract: Identifying and understanding patterns in movement data are amongst the principal aims of movement ecology. By quantifying the similarity of movement trajectories, inferences can be made about diverse processes, ranging from individual specialisation to the ontogeny of foraging strategies. Movement analysis is not unique to ecology however, and methods for estimating the similarity of movement trajectories have been developed in other fields but are currently under-utilised by ecologists. Here, we introduce five commonly used measures of trajectory similarity: dynamic time warping (DTW), longest common subsequence (LCSS), edit distance for real sequences (EDR), Fréchet distance and nearest neighbour distance (NND), of which only NND is routinely used by ecologists. We investigate the performance of each of these measures by simulating movement trajectories using an Ornstein-Uhlenbeck (OU) model in which we varied the following parameters: (1) the point of attraction, (2) the strength of attraction to this point and (3) the noise or volatility added to the movement process in order to determine which measures were most responsive to such changes. In addition, we demonstrate how these measures can be applied using movement trajectories of breeding northern gannets (Morus bassanus) by performing trajectory clustering on a large ecological dataset. Simulations showed that DTW and Fréchet distance were most responsive to changes in movement parameters and were able to distinguish between all the different parameter combinations we trialled. In contrast, NND was the least sensitive measure trialled. When applied to our gannet dataset, the five similarity measures were highly correlated despite differences in their underlying calculation. Clustering of trajectories within and across individuals allowed us to easily visualise and compare patterns of space use over time across a large dataset. Trajectory clusters reflected the bearing on which birds departed the colony and highlighted the use of well-known bathymetric features. As both the volume of movement data and the need to quantify similarity amongst animal trajectories grow, the measures described here and the bridge they provide to other fields of research will become increasingly useful in ecology. Significance statement: As the use of tracking technology increases, there is a need to develop analytical techniques to process such large volumes of data. One area in which this would be useful is the comparison of individual movement trajectories. In response, a variety of measures of trajectory similarity have been developed within the information sciences. However, such measures are rarely used by ecologists who may be unaware of them. To remedy this, we apply five common measures of trajectory similarity to both simulated data and real ecological dataset comprising of movement trajectories of breeding northern gannets. Dynamic time warping and Fréchet distance performed best on simulated data. Using trajectory similarity measures on our gannet dataset, we identified distinct foraging clusters centred on different bathymetric features, demonstrating one application of such similarity measures. As new technology and analysis techniques proliferate across ecology and the information sciences, closer ties between these fields promise further innovative analysis of movement data.
Abstract.
2018
Blount J, Plummer K, Bearhop S, leech D, chamberlain D (2018). Effects of winter food provisioning on the phenotypes of breeding blue tits. Ecology and Evolution
Bodey TW, Cleasby IR, Votier SC, Hamer KC, Newton J, Patrick SC, Wakefield ED, Bearhop S (2018). Frequency and consequences of individual dietary specialisation in a wide-ranging marine predator, the northern gannet.
MARINE ECOLOGY PROGRESS SERIES,
604, 251-262.
Author URL.
Soriano-Redondo A, Bearhop S, Lock L, Votier SC, Hilton GM (2018). Internet-based monitoring of public perception of conservation. Proceedings of the 5th European Congress of Conservation Biology.
Perkins MJ, Inger R, Bearhop S, Sanders D (2018). Multichannel feeding by spider functional groups is driven by feeding strategies and resource availability.
Oikos,
127(1), 23-33.
Abstract:
Multichannel feeding by spider functional groups is driven by feeding strategies and resource availability
Multichannel feeding, whereby consumers feed across resource channels such as upon herbivore and detritivore resources, acts to link discrete compartments of a food web with implications for ecosystem functioning and stability. Currently however, we have little understanding which feeding strategies of consumers underlie multichannel feeding. We therefore link spider functional group and resource density-dependent or density-independent feeding strategies to multichannel feeding by quantifying not only consumer diet, but also the relative availability of resources. Here we analysed herbivore (green) and detritivore (brown) prey use by spider communities in grasslands, and tested if available prey biomass proportions were linked to observed spider dietary proportions. Different spider functional groups each linked green and brown resource channels, but while green prey were always consumed in proportion to their relative biomass, brown prey were consumed independently of proportion by some functional groups. Additionally, we found greater intraguild predation by cursorial spiders when green resources were relatively scarcer, suggesting green prey was preferred, and needed to be compensated for when rare. Overall, we observed a stronger consumer connection to the green than brown resource channel, yet this green connection was more variable due to greater range in green resource availability across grasslands and density-dependent consumption on green prey. Consequently, multichannel feeding by spiders was determined by density-dependent and density-independent feeding strategies that varied by spider functional group and across resources channels. Our results demonstrate that the role of multichannel feeding by spiders in linking separate food web compartments is a dynamic component of food web structure in these wild grasslands.
Abstract.
Healy K, Guillerme T, Kelly SBA, Inger R, Bearhop S, Jackson AL (2018). SIDER: an R package for predicting trophic discrimination factors of consumers based on their ecology and phylogenetic relatedness.
Ecography,
41(8), 1393-1400.
Abstract:
SIDER: an R package for predicting trophic discrimination factors of consumers based on their ecology and phylogenetic relatedness
Stable isotope mixing models (SIMMs) are an important tool used to study species' trophic ecology. These models are dependent on, and sensitive to, the choice of trophic discrimination factors (TDF) representing the offset in stable isotope delta values between a consumer and their food source when they are at equilibrium. Ideally, controlled feeding trials should be conducted to determine the appropriate TDF for each consumer, tissue type, food source, and isotope combination used in a study. In reality however, this is often not feasible nor practical. In the absence of species-specific information, many researchers either default to an average TDF value for the major taxonomic group of their consumer, or they choose the nearest phylogenetic neighbour for which a TDF is available. Here, we present the SIDER package for R, which uses a phylogenetic regression model based on a compiled dataset to impute (estimate) a TDF of a consumer. We apply information on the tissue type and feeding ecology of the consumer, all of which are known to affect TDFs, using Bayesian inference. Presently, our approach can estimate TDFs for two commonly used isotopes (nitrogen and carbon), for species of mammals and birds with or without previous TDF information. The estimated posterior probability provides both a mean and variance, reflecting the uncertainty of the estimate, and can be subsequently used in the current suite of SIMM software. SIDER allows users to place a greater degree of confidence on their choice of TDF and its associated uncertainty, thereby leading to more robust predictions about trophic relationships in cases where study-specific data from feeding trials is unavailable. The underlying database can be updated readily to incorporate more stable isotope tracers, replicates and taxonomic groups to further increase the confidence in dietary estimates from stable isotope mixing models, as this information becomes available.
Abstract.
Bennison A, Bearhop S, Bodey TW, Votier SC, Grecian WJ, Wakefield ED, Hamer KC, Jessopp M (2018). Search and foraging behaviors from movement data: a comparison of methods.
Ecology and Evolution,
8(1), 13-24.
Abstract:
Search and foraging behaviors from movement data: a comparison of methods
Search behavior is often used as a proxy for foraging effort within studies of animal movement, despite it being only one part of the foraging process, which also includes prey capture. While methods for validating prey capture exist, many studies rely solely on behavioral annotation of animal movement data to identify search and infer prey capture attempts. However, the degree to which search correlates with prey capture is largely untested. This study applied seven behavioral annotation methods to identify search behavior from GPS tracks of northern gannets (Morus bassanus), and compared outputs to the occurrence of dives recorded by simultaneously deployed time–depth recorders. We tested how behavioral annotation methods vary in their ability to identify search behavior leading to dive events. There was considerable variation in the number of dives occurring within search areas across methods. Hidden Markov models proved to be the most successful, with 81% of all dives occurring within areas identified as search. k-Means clustering and first passage time had the highest rates of dives occurring outside identified search behavior. First passage time and hidden Markov models had the lowest rates of false positives, identifying fewer search areas with no dives. All behavioral annotation methods had advantages and drawbacks in terms of the complexity of analysis and ability to reflect prey capture events while minimizing the number of false positives and false negatives. We used these results, with consideration of analytical difficulty, to provide advice on the most appropriate methods for use where prey capture behavior is not available. This study highlights a need to critically assess and carefully choose a behavioral annotation method suitable for the research question being addressed, or resulting species management frameworks established.
Abstract.
2017
Weegman MD, Fox AD, Hilton GM, Hodgson DJ, Walsh AJ, Griffin LR, Bearhop S (2017). Diagnosing the decline of the Greenland White-fronted Goose Anser albifrons flavirostris using population and individual level techniques.
Wildfowl,
67, 3-18.
Abstract:
Diagnosing the decline of the Greenland White-fronted Goose Anser albifrons flavirostris using population and individual level techniques
Following an increase in numbers from 1982 to 1998, the Greenland White-fronted Goose Anser albifrons flavirostris declined over the period 1999–2015, stimulating detailed analyses at the population and individual level to provide a better understanding of the dynamics of this subspecies. Here we synthesise the results of the analyses in order to describe the potential reasons for the decline. Utilising a 27-year capture-mark-recapture dataset from the main wintering site for these birds (Wexford, Ireland), multistate models estimated sex-specific survival and movement probabilities. Our results suggested no evidence of a sex bias in emigration or “remigration” rates. These analyses formed the foundation for an integrated population model (IPM), which included population size and productivity data to assess source-sink dynamics of Wexford birds through estimation of age-, site-, and year-specific survival and movement probabilities. Results from the IPM suggested that Wexford is a large sink, and that a reduction in productivity is an important demographic mechanism underlying population change for birds wintering at the site. Low productivity may be due to environmental conditions in the breeding range, because birds bred successfully at youngest ages when conditions in Greenland were favourable in the year(s) during adulthood prior to and including the year of successful breeding. This effect could be mediated by prolonged parent-offspring relationships, as birds remained with parents into adulthood, forfeiting immediate reproductive success despite there being no fitness benefits to offspring of family associations after age 3 years. Global Positioning System and acceleration data collected from 15 male individuals suggested that two successful breeding birds were the only tagged individuals whose mate exhibited prolonged incubation. More data is required, however, to determine whether poor productivity is attributable to deferral of nesting or to failure of nesting attempts. Spring foraging did not appear to limit breeding or migration distance because breeding and non-breeding or failed-breeding birds, as well as Irish and Scottish birds, did not differ in their proportion of time spent feeding or on energy expenditure in spring. We recommend that future research should quantify the demography of other Greenland White-fronted Goose wintering flocks, to assess holistically the mechanisms underlying the global population decline.
Abstract.
Swan GJF, Redpath SM, Bearhop S, McDonald RA (2017). Ecology of Problem Individuals and the Efficacy of Selective Wildlife Management.
Trends Ecol Evol,
32(7), 518-530.
Abstract:
Ecology of Problem Individuals and the Efficacy of Selective Wildlife Management.
As a result of ecological and social drivers, the management of problems caused by wildlife is becoming more selective, often targeting specific animals. Narrowing the sights of management relies upon the ecology of certain 'problem individuals' and their disproportionate contribution to impacts upon human interests. We assess the ecological evidence for problem individuals and confirm that some individuals or classes can be both disproportionately responsible and more likely to reoffend. The benefits of management can sometimes be short-lived, and selective management can affect tolerance of wildlife for better or worse, but, when effectively targeted, selective management can bring benefits by mitigating impact and conflict, often in a more socially acceptable way.
Abstract.
Author URL.
Parr N, Bearhop S, Douglas DC, Takekawa JY, Prosser DJ, Newman SH, Perry WM, Balachandran S, Witt MJ, Hou Y, et al (2017). High altitude flights by ruddy shelduck Tadorna ferruginea during trans-Himalayan migrations.
Journal of Avian Biology,
48(10), 1310-1315.
Abstract:
High altitude flights by ruddy shelduck Tadorna ferruginea during trans-Himalayan migrations
Birds that migrate across high altitude mountain ranges are faced with the challenge of maintaining vigorous exercise in environments with limited oxygen. Ruddy shelducks are known to use wintering grounds south of the Tibetan Plateau at sea level and breeding grounds north of Himalayan mountain range. Therefore, it is likely these shelducks are preforming high altitude migrations. In this study we analyse satellite telemetry data collected from 15 ruddy shelduck from two populations wintering south of the Tibetan Plateau from 2007 to 2011. During north and south migrations ruddy shelduck travelled 1481 km (range 548–2671 km) and 1238 km (range 548–2689 km) respectively. We find mean maximum altitudes of birds in flight reached 5590 m (range of means 4755–6800 m) and mean maximum climb rates of 0.45 m s–1 (range 0.23–0.74 m s–1). The ruddy shelduck is therefore an extreme high altitude migrant that has likely evolved a range of physiological adaptations in order to complete their migrations.
Abstract.
Soriano-Redondo A, Bearhop S, Lock L, Votier SC, Hilton GM (2017). Internet-based monitoring of public perception of conservation.
Biological Conservation,
206, 304-309.
Abstract:
Internet-based monitoring of public perception of conservation
Monitoring public perception of conservation is essential to ensure successful conservation outcomes. However, evaluating attitudes towards conservation projects presents daunting challenges because it is time consuming, expensive and open to social biases and small sample-size errors. Here, we present a recently developed approach to overcome these limitations – Internet-based methods - in particular offsite and onsite metrics. Offsite methods refer to Internet data mining tools that extract Internet search queries, such as Google Trends, while onsite methods refer to programmes that monitor traffic within websites, such as Google Analytics. We explore the potential of these methods rather than focus on the particular details of the case-studies provided to illustrate them. We used offsite methods to determine patterns in public interest in a reintroduced flagship species and in conservation awareness projects in the UK. We employed onsite metrics to assess the success in communicating a conservation outcome and to evaluate the success in online public engagement of a conservation NGO. Our results indicate that both offsite and onsite metrics are able to track changes in public interest across time and space. In particular, onsite metrics provide high levels of temporal and spatial resolution with a high degree of flexibility. These tools could add reliable information to traditional social surveys and represent an opportunity to improve our understanding of the drivers of interest in conservation.
Abstract.
Healy K, Kelly SBA, Guillerme T, Inger R, Bearhop S, Jackson AL (2017). Predicting trophic discrimination factor using Bayesian inference and phylogenetic, ecological and physiological data. DEsIR: Discrimination Estimation in R. , 5
Healy K, Kelly SBA, Guillerme T, Inger R, Bearhop S, Jackson AL (2017). Predicting trophic discrimination factor using Bayesian inference and phylogenetic, ecological and physiological data. DEsIR: Discrimination Estimation in R. , 5
Weegman MD, Bearhop S, Hilton GM, Walsh AJ, Griffin L, Resheff YS, Nathan R, Fox AD (2017). Using accelerometry to compare costs of extended migration in an arctic herbivore.
CURRENT ZOOLOGY,
63(6), 667-674.
Author URL.
2016
Moreno R, Stowasser G, McGill RAR, Bearhop S, Phillips RA (2016). Assessing the structure and temporal dynamics of seabird communities: the challenge of capturing marine ecosystem complexity.
J Anim Ecol,
85(1), 199-212.
Abstract:
Assessing the structure and temporal dynamics of seabird communities: the challenge of capturing marine ecosystem complexity.
Understanding interspecific interactions, and the influences of anthropogenic disturbance and environmental change on communities, are key challenges in ecology. Despite the pressing need to understand these fundamental drivers of community structure and dynamics, only 17% of ecological studies conducted over the past three decades have been at the community level. Here, we assess the trophic structure of the procellariiform community breeding at South Georgia, to identify the factors that determine foraging niches and possible temporal changes. We collected conventional diet data from 13 sympatric species between 1974 and 2002, and quantified intra- and inter-guild, and annual variation in diet between and within foraging habits. In addition, we tested the reliability of stable isotope analysis (SIA) of seabird feathers collected over a 13-year period, in relation to those of their potential prey, as a tool to assess community structure when diets are diverse and there is high spatial heterogeneity in environmental baselines. Our results using conventional diet data identified a four-guild community structure, distinguishing species that mainly feed on crustaceans; large fish and squid; a mixture of crustaceans, small fish and squid; or carrion. In total, Antarctic krill Euphausia superba represented 32%, and 14 other species a further 46% of the combined diet of all 13 predators, underlining the reliance of this community on relatively few types of prey. Annual variation in trophic segregation depended on relative prey availability; however, our data did not provide evidence of changes in guild structure associated with a suggested decline in Antarctic krill abundance over the past 40 years. Reflecting the differences in δ(15) N of potential prey (crustaceans vs. squid vs. fish and carrion), analysis of δ(15) N in chick feathers identified a three-guild community structure that was constant over a 13-year period, but lacked the trophic cluster representing giant petrels which was identified using conventional diet data. Our study is the first in recent decades to examine dietary changes in seabird communities over time. Conventional dietary analysis provided better resolution of community structure than SIA. However, δ(15) N in chick feathers, which reflected trophic (level) specialization, was nevertheless an effective and less time-consuming means of monitoring temporal changes.
Abstract.
Author URL.
Weegman MD, Bearhop S, Hilton GM, Walsh A, Fox AD (2016). Conditions during adulthood affect cohort-specific reproductive success in an Arctic-nesting goose population.
PeerJ,
4Abstract:
Conditions during adulthood affect cohort-specific reproductive success in an Arctic-nesting goose population.
Variation in fitness between individuals in populations may be attributed to differing environmental conditions experienced among birth (or hatch) years (i.e. between cohorts). In this study, we tested whether cohort fitness could also be explained by environmental conditions experienced in years post-hatch, using 736 lifelong resighting histories of Greenland white-fronted geese (Anser albifrons flavirostris) marked in their first winter. Specifically, we tested whether variation in age at first successful reproduction, the size of the first successful brood and the proportion of successful breeders by cohort was explained by environmental conditions experienced on breeding areas in west Greenland during hatch year, those in adulthood prior to successful reproduction and those in the year of successful reproduction, using North Atlantic Oscillation indices as proxies for environmental conditions during these periods. Fifty-nine (8%) of all marked birds reproduced successfully (i.e. were observed on wintering areas with young) only once in their lifetime and 15 (2%) reproduced successfully twice or thrice. Variation in age at first successful reproduction was explained by the environmental conditions experienced during adulthood in the years prior to successful reproduction. Birds bred earliest (mean age 4) when environmental conditions were 'good' prior to the year of successful reproduction. Conversely, birds successfully reproduced at older ages (mean age 7) if they experienced adverse conditions prior to the year of successful reproduction. Hatch year conditions and an interaction between those experienced prior to and during the year of successful reproduction explained less (marginally significant) variation in age at first successful reproduction. Environmental conditions did not explain variation in the size of the first successful brood or the proportion of successful breeders. These findings show that conditions during adulthood prior to the year of successful reproduction are most important in determining the age at first successful reproduction in Greenland white-fronted geese. Very few birds bred successfully at all (most only once), which suggests that May environmental conditions on breeding areas have cohort effects that influence lifetime (and not just annual) reproductive success.
Abstract.
Author URL.
Soriano-Redondo A, Bearhop S, Cleasby IR, Lock L, Votier SC, Hilton GM (2016). Ecological Responses to Extreme Flooding Events: a Case Study with a Reintroduced Bird.
Sci Rep,
6Abstract:
Ecological Responses to Extreme Flooding Events: a Case Study with a Reintroduced Bird.
In recent years numerous studies have documented the effects of a changing climate on the world's biodiversity. Although extreme weather events are predicted to increase in frequency and intensity and are challenging to organisms, there are few quantitative observations on the survival, behaviour and energy expenditure of animals during such events. We provide the first data on activity and energy expenditure of birds, Eurasian cranes Grus grus, during the winter of 2013-14, which saw the most severe floods in SW England in over 200 years. We fitted 23 cranes with telemetry devices and used remote sensing data to model flood dynamics during three consecutive winters (2012-2015). Our results show that during the acute phase of the 2013-14 floods, potential feeding areas decreased dramatically and cranes restricted their activity to a small partially unflooded area. They also increased energy expenditure (+15%) as they increased their foraging activity and reduced resting time. Survival did not decline in 2013-14, indicating that even though extreme climatic events strongly affected time-energy budgets, behavioural plasticity alleviated any potential impact on fitness. However under climate change scenarios such challenges may not be sustainable over longer periods and potentially could increase species vulnerability.
Abstract.
Author URL.
Weegman MD, Bearhop S, Fox AD, Hilton GM, Walsh AJ, McDonald JL, Hodgson DJ (2016). Integrated population modelling reveals a perceived source to be a cryptic sink.
J Anim Ecol,
85(2), 467-475.
Abstract:
Integrated population modelling reveals a perceived source to be a cryptic sink.
Demographic links among fragmented populations are commonly studied as source-sink dynamics, whereby source populations exhibit net recruitment and net emigration, while sinks suffer net mortality but enjoy net immigration. It is commonly assumed that large, persistent aggregations of individuals must be sources, but this ignores the possibility that they are sinks instead, buoyed demographically by immigration. We tested this assumption using Bayesian integrated population modelling of Greenland white-fronted geese (Anser albifrons flavirostris) at their largest wintering site (Wexford, Ireland), combining capture-mark-recapture, census and recruitment data collected from 1982 to 2010. Management for this subspecies occurs largely on wintering areas; thus, study of source-sink dynamics of discrete regular wintering units provides unprecedented insights into population regulation and enables identification of likely processes influencing population dynamics at Wexford and among 70 other Greenland white-fronted goose wintering subpopulations. Using results from integrated population modelling, we parameterized an age-structured population projection matrix to determine the contribution of movement rates (emigration and immigration), recruitment and mortality to the dynamics of the Wexford subpopulation. Survival estimates for juvenile and adult birds at Wexford and adult birds elsewhere fluctuated over the 29-year study period, but were not identifiably different. However, per capita recruitment rates at Wexford in later years (post-1995) were identifiably lower than in earlier years (pre-1995). The observed persistence of the Wexford subpopulation was only possible with high rates of immigration, which exceeded emigration in each year. Thus, despite its apparent stability, Wexford has functioned as a sink over the entire study period. These results demonstrate that even large subpopulations can potentially be sinks, and that movement dynamics (e.g. immigration) among winters can dramatically obscure key processes driving subpopulation size. Further, novel population models which integrate capture-mark-recapture, census and recruitment data are essential to correctly ascribing source-sink status and accurately informing development of site-safeguard networks.
Abstract.
Author URL.
Healy K, Kelly SBA, Guillerme T, Inger R, Bearhop S, Jackson AL (2016). Predicting trophic discrimination factor using Bayesian inference and phylogenetic, ecological and physiological data. DEsIR: Discrimination Estimation in R. , 4
Catry P, Campos AR, Granadeiro JP, Neto JM, Ramos J, Newton J, Bearhop S (2016). Provenance does matter: links between winter trophic segregation and the migratory origins of European robins.
Oecologia,
182(4), 985-994.
Abstract:
Provenance does matter: links between winter trophic segregation and the migratory origins of European robins.
Amongst migratory species, it is common to find individuals from different populations or geographical origins sharing staging or wintering areas. Given their differing life histories, ecological theory would predict that the different groups of individuals should exhibit some level of niche segregation. This has rarely been investigated because of the difficulty in assigning migrating individuals to breeding areas. Here, we start by documenting a broad geographical gradient of hydrogen isotopes (δ 2H) in robin Erithacus rubecula feathers across Europe. We then use δ 2H, as well as wing-tip shape, as surrogates for broad migratory origin of birds wintering in Iberia, to investigate the ecological segregation of populations. Wintering robins of different sexes, ages and body sizes are known to segregate between habitats in Iberia. This has been attributed to the despotic exclusion of inferior competitors from the best patches by dominant individuals. We find no segregation between habitats in relation to δ 2H in feathers, or to wing-tip shape, which suggests that no major asymmetries in competitive ability exist between migrant robins of different origins. Trophic level (inferred from nitrogen isotopes in blood) correlated both with δ 2H in feathers and with wing-tip shape, showing that individuals from different geographic origins display a degree of ecological segregation in shared winter quarters. Isotopic mixing models indicate that wintering birds originating from more northerly populations consume more invertebrates. Our multi-scale study suggests that trophic-niche segregation may result from specializations (arising in the population-specific breeding areas) that are transported by the migrants into the shared wintering grounds.
Abstract.
Author URL.
Saporiti F, Bearhop S, Vales DG, Silva L, Zenteno L, Tavares M, Crespo EA, Cardona L (2016). Resource partitioning among air-breathing marine predators: are body size and mouth diameter the major determinants?.
Marine Ecology,
37(5), 957-969.
Abstract:
Resource partitioning among air-breathing marine predators: are body size and mouth diameter the major determinants?
Although the body size of consumers may be a determinant factor in structuring food webs, recent evidence indicates that body size may fail to fully explain differences in the resource use patterns of predators in some situations. Here we compared the trophic niche of three sympatric and sexually dimorphic air-breathing marine predators (the South American sea lion, Otaria flavescens, the South American fur seal, Arctocephalus australis, and the Magellanic penguin, Spheniscus magellanicus) in three areas of the Southwestern Atlantic Ocean (Río de la Plata and adjoining areas, Northern Patagonia and Southern Patagonia), in order to assess the importance of body size and mouth diameter in determining resource partitioning. Body weight and palate/bill breadth were used to characterize the morphology of each sex and species, whereas the trophic niche was assessed through the use of stable isotope ratios of carbon and nitrogen. The quantitative method Stable Isotope Bayesian Ellipses in R (SIBER) was used to compute the area of the Bayesian ellipses and the overlap of the isotopic niches. The results showed that morphological similarity was significantly correlated with isotopic distance between groups within the δ13C–δ15N bi-plot space in the Río de la Plata area, but not in Northern and Southern Patagonia. Furthermore, resource partitioning between groups changed regionally, and some morphologically distinct groups exhibited a large trophic overlap in certain areas, such as the case of male penguins and male sea lions in Southern Patagonia. Conversely, female sea lions always overlapped with the much larger males of the same species, but never overlapped with the morphologically similar male fur seals. These results indicate that body size and mouth diameter are just two of the factors involved in resource partitioning within the guild of air-breathing predators considered here, and for whom – under certain environmental conditions – other factors are more important than morphology.
Abstract.
Weegman MD, Bearhop S, Hilton GM, Walsh AJ, Weegman KM, Hodgson DJ, Fox AD (2016). Should I stay or should I go? Fitness costs and benefits of prolonged parent-offspring and sibling-sibling associations in an Arctic-nesting goose population.
Oecologia,
181(3), 809-817.
Abstract:
Should I stay or should I go? Fitness costs and benefits of prolonged parent-offspring and sibling-sibling associations in an Arctic-nesting goose population.
Theory predicts persistence of long-term family relationships in vertebrates will occur until perceived fitness costs exceed benefits to either parents or offspring. We examined whether increased breeding probability and survival were associated with prolonged parent-offspring and sibling-sibling relationships in a long-lived Arctic migrant herbivore, the Greenland white-fronted goose (Anser albifrons flavirostris). Although offspring associated with parents for 1-13 years, 79 % of these associations lasted two or less years. Only 65 (9.9 %) of the 656 marked offspring bred once in their lifetime, and just 16 (2.4 %) bred twice or more. The probability of birds with siblings breeding successfully in a subsequent year was credibly greater than that of independent birds at ages 5, 6, and 7. Survival of offspring with parents was credibly greater than that of independent/nonbreeder birds at all possible ages (i.e. ages 2-7+). A cost-benefit matrix model utilizing breeding and survival probabilities showed that staying with family groups was favored over leaving until age 3, after which there were no credible differences between staying and leaving strategies until the oldest ages, when leaving family groups was favored. Thus, most birds in this study either departed family groups early (e.g. at age 2, when the "stay" strategy was favored) or as predicted by our cost-benefit model (i.e. at age 3). Although extended family associations are a feature of this population, we contend that the survival benefits are not sufficient enough to yield clear fitness benefits, and associations only persist because parents and offspring mutually benefit from their persistence.
Abstract.
Author URL.
Votier SC, Aspinall S, Bearhop S, Bilton D, Newton J, Alström P, Leader P, Carey G, Furnes RW, Olsson U, et al (2016). Stable isotopes and mtDNA reveal niche segregation but no evidence of intergradation along a habitat gradient in the Lesser Whitethroat complex (Sylvia curruca; Passeriformes; Aves).
Journal of Ornithology,
157(4), 1017-1027.
Abstract:
Stable isotopes and mtDNA reveal niche segregation but no evidence of intergradation along a habitat gradient in the Lesser Whitethroat complex (Sylvia curruca; Passeriformes; Aves)
Niche segregation plays a critical role in the speciation process, but determining the extent to which taxa are geographically or ecologically isolated is challenging. In this study, we use stable isotopes of carbon (δ13C), nitrogen (δ15N), hydrogen (δ2H) and oxygen (δ18O) to test for ecological differences among taxa in the Lesser Whitethroat Sylvia curruca complex. Analysis of mitochondrial DNA (mtDNA) revealed 6 distinct haplotype groups, which conform to at least 5 distinct taxa. Stable isotopes provided insight into geographical and broad-scale ecological differences among haplotypes. The most striking isotope differences were between the populations inhabiting Siberian boreal forest (S. c. blythi) from the one inhabiting semi-desert in Kazakhstan (S. c. halimodendri). It is generally assumed that these two populations form a morphological cline along a gradient from mesic to xeric habitat. Our sample includes a large proportion of morphologically intermediate individuals that appear to represent a hybrid population. However, in all of these, there is strict correspondence between haplotype and isotope signature, suggesting an ecological division on the breeding grounds between all our samples of these two taxa. The lack of ecologically intermediate individuals among our sample of morphologically intermediate ones thus speaks against the existence of a cline. The two taxa blythi and halimodendri emerge as potential models for the study of the early stages of the speciation process. While differences in stable isotopes may be largely influenced by geography, we also demonstrate how, in specific instances (such as the alleged cline reported here), they may be used to evaluate niche segregation between taxa, providing information of importance for determination of species limits.
Abstract.
Catry T, Lourenco PM, Lopes RJ, Bocher P, Carneiro C, Alves JA, Delaporte P, Bearhop S, Piersma T, Granadeiro JP, et al (2016). Use of stable isotope fingerprints to assign wintering origin and trace shorebird movements along the East Atlantic Flyway.
BASIC AND APPLIED ECOLOGY,
17(2), 177-187.
Author URL.
Newth JL, Rees EC, Cromie RL, McDonald RA, Bearhop S, Pain DJ, Norton GJ, Deacon C, Hilton GM (2016). Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain.
Environ Pollut,
209, 60-67.
Abstract:
Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain.
Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity and mortality in waterbirds globally, but the thresholds at which blood levels begin to affect the physiology of birds in the wild are less well known. Here we determine the prevalence of lead exposure in whooper swans and, for the first time, identify the level of blood lead associated with initial reductions in body condition. Blood lead elevated above background levels (i.e. >20 μg dL(-1)) was found in 41.7% (125/300) of swans tested. Blood lead was significantly negatively associated with winter body condition when levels were ≥44 μg dL(-1) (27/260 = 10%). Our findings indicating that sub-lethal impacts of lead on body condition occur at the lower end of previously established clinical thresholds and that a relatively high proportion of individuals in this population may be affected, reaffirm the importance of reducing contamination of the environment with lead shot.
Abstract.
Author URL.
2015
Patrick SC, Bearhop S, Bodey TW, Grecian WJ, Hamer KC, Lee J, Votier SC (2015). Individual seabirds show consistent foraging strategies in response to predictable fisheries discards.
JOURNAL OF AVIAN BIOLOGY,
46(5), 431-440.
Author URL.
Agnew A, Wang J, Fanning S, Bearhop S, McMahon BJ (2015). Insights into antimicrobial resistance among long distance migratory East Canadian High Arctic light-bellied Brent geese (Branta bernicla hrota).
Ir Vet J,
69Abstract:
Insights into antimicrobial resistance among long distance migratory East Canadian High Arctic light-bellied Brent geese (Branta bernicla hrota).
BACKGROUND: Antimicrobial resistance (AMR) is the most significant threat to global public health and ascertaining the role wild birds play in the epidemiology of resistance is critically important. This study investigated the prevalence of AMR Gram-negative bacteria among long-distance migratory East Canadian High Arctic (ECHA) light-bellied Brent geese found wintering on the east coast of Ireland. FINDINGS: in this study a number of bacterial species were isolated from cloacal swabs taken from ECHA light-bellied Brent geese. Nucleotide sequence analysis identified five species of Gram-negative bacteria; the dominant isolated species were Pantoea spp. (n = 5) followed by Buttiauxella agrestis (n = 2). Antimicrobial susceptibility disk diffusion results identified four of the Pantoea spp. strains, and one of the Buttiauxella agrestis strains resistant to amoxicillin-clavulanic acid. CONCLUSION: to our knowledge this is the first record of AMR bacteria isolated from long distance migratory ECHA light-bellied Brent geese. This indicates that this species may act as reservoirs and potential disseminators of resistance genes into remote natural ecosystems across their migratory range. This population of geese frequently forage (and defecate) on public amenity areas during the winter months presenting a potential human health risk.
Abstract.
Author URL.
Saporiti F, Bearhop S, Vales DG, Silva L, Zenteno L, Tavares M, Crespo EA, Cardona L (2015). Latitudinal changes in the structure of marine food webs in the Southwestern Atlantic Ocean.
Marine Ecology Progress Series,
538, 23-34.
Abstract:
Latitudinal changes in the structure of marine food webs in the Southwestern Atlantic Ocean
Food chain length is known to increase with primary productivity, species richness and environmental stability. Primary productivity and species richness decrease poleward at mid and high latitudes in the Southwestern Atlantic, and hence food chain length of coastal ecosystems is expected to decrease poleward, unless seasonal changes in water temperature destabilise food webs at mid latitude. We used stable isotopes of carbon and nitrogen and SIBER (Stable Isotope Bayesian Ellipses in R) to determine the food chain length and other patterns of interconnections (i.e. topology) of coastal food webs from 3 contrasting regions: the temperate estuarine zone associated with the Río de la Plata plume, the tidal zone off northern and central Patagonia, and the cold estuarine zone off southern Patagonia. Results indicate that food chain length decreases and trophic redundancy increases as latitude increases in all of the compartments of the food web considered. This is in agreement with results emerging from reconstructions of marine food web length during the late Holocene in the same regions, thus suggesting that they are not artefacts caused by the intense exploitation of top predators in the region since European settlement. Furthermore, differences in primary productivity do not fully explain the observed patterns. Instead, we argue that the latitudinal reduction of species diversity reported for the Southwestern Atlantic may be the primary reason for the observed pattern. The reduction in the diversity of forage fishes and squids at high latitude is proposed to result into a wasp-waist ecosystem, characterised by a high trophic redundancy at high trophic levels.
Abstract.
Wakefield ED, Cleasby IR, Bearhop S, Bodey TW, Davies RD, Miller PI, Newton J, Votier SC, Hamer KC (2015). Long-term individual foraging site fidelitywhy some gannets don't change their spots.
ECOLOGY,
96(11), 3058-3074.
Author URL.
Weegman MD, Fox AD, Bearhop S, Hilton GM, Walsh AJ, Cleasby IR, Hodgson DJ (2015). No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population.
Ibis,
157(2), 401-405.
Abstract:
No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population
Understanding movement of individuals between sites is necessary to quantify emigration and immigration, yet previous analyses exploring sex biases in site fidelity among birds have not evaluated remigration (the return of marked birds that moved to alternative areas from the site at which they were marked). Using novel Bayesian multistate models, we tested whether between-winter emigration, remigration and survival rates were sex-biased among 851 Greenland White-fronted Geese Anser albifrons flavirostris marked at Wexford, Ireland. We found no evidence for sex biases in emigration, remigration or survival. Thus, sex biases in winter site fidelity do not occur in any form in this population; these techniques for modelling sex-biased movement will be useful for a better understanding of site fidelity and connectivity in other marked animal populations.
Abstract.
Weegman MD, Fox AD, Bearhop S, Hilton GM, Walsh AJ, Cleasby IR, Hodgson DJ (2015). No evidence for sex bias in winter inter-site movements in an Arctic-nesting goose population. Ibis
Moussy C, Atterby H, Griffiths AGF, Allnutt TR, Mathews F, Smith GC, Aegerter JN, Bearhop S, Hosken DJ (2015). Population genetic structure of serotine bats (Eptesicus serotinus) across Europe and implications for the potential spread of bat rabies (European bat lyssavirus EBLV-1).
HEREDITY,
115(1), 83-92.
Author URL.
Robertson A, McDonald RA, Delahay RJ, Kelly SD, Bearhop S (2015). Resource availability affects individual niche variation and its consequences in group-living European badgers Meles meles.
Oecologia,
178(1), 31-43.
Abstract:
Resource availability affects individual niche variation and its consequences in group-living European badgers Meles meles.
Although intra-population variation in niches is a widespread phenomenon with important implications for ecology, evolution and management of a range of animal species, the causes and consequences of this variation remain poorly understood. We used stable isotope analysis to characterise foraging niches and to investigate the causes and consequences of individual niche variation in the European badger, a mustelid mammal that lives in territorial social groups, but forages alone. We found that the degree of individual niche variation within social groups was negatively related to the availability of farmland habitats, which represent an important foraging habitat for badgers; and was positively related to territory size, supporting the idea that resource limitation and ecological opportunity lead to increased individual specialisation. We also found that the degree of individual specialisation related to an individual's body condition and that this effect varied with ecological context; such that specialisation had a stronger positive relationship with body condition in social groups with reduced availability of key farmland habitats. Body condition was also related to the utilisation of specific resources (woodland invertebrates), but again this relationship varied with the availability of farmland foraging habitats. This study supports the idea that resource availability plays an important role in determining patterns of individual niche variation, and identifies the potential adaptive consequences of specialised foraging strategies.
Abstract.
Author URL.
Cleasby IR, Wakefield ED, Bodey TW, Davies RD, Patrick SC, Newton J, Votier SC, Bearhop S, Hamer KC (2015). Sexual segregation in a wide-ranging marine predator is a consequence of habitat selection.
Marine Ecology Progress Series,
518, 1-12.
Abstract:
Sexual segregation in a wide-ranging marine predator is a consequence of habitat selection
Sexual segregation, common in many species, is usually attributed to intra-specific competition or habitat choice. However, few studies have simultaneously quantified sex-specific foraging behaviour and habitat use. We combined movement, diving, stable isotope and oceanographic data to test whether sexual segregation in northern gannets Morus bassanus results from sex-specific habitat use. Breeding birds foraging in a seasonally stratified shelf sea were tracked over 3 consecutive breeding seasons (2010-2012). Females made longer trips, foraged farther offshore and had lower δ13C values than males. Male and female foraging areas overlapped only slightly. Males foraged more in mixed coastal waters, where net primary production (NPP) was relatively high (>3 mg C m-2 d-1) and sea-surface temperature (SST) was relatively low (15°C) more than females, possibly as a consequence of foraging in productive mixed waters over offshore banks. Females foraged most frequently in stratified offshore waters, of intermediate SST (12-15°C), but exhibited no consistent response to NPP. Sex-specific differences in diving behaviour corresponded with differences in habitat use: males made more long and deep U-shaped dives. Such dives were characteristic of inshore foraging, whereas shorter and shallower V-shaped dives occurred more often in offshore waters. Heavier birds attained greater depths during V-shaped dives, but even when controlling for body mass, females made deeper V-shaped dives than males. Together, these results indicate that sexual segregation in gannets is driven largely by habitat segregation between mixed and stratified waters, which in turn results in sex-specific foraging behaviour and dive depths.
Abstract.
Catry T, Lourenço PM, Lopes RJ, Carneiro C, Alves JA, Costa J, Rguibi-Idrissi H, Bearhop S, Piersma T, Granadeiro JP, et al (2015). Structure and functioning of intertidal food webs along an avian flyway: a comparative approach using stable isotopes.
Functional EcologyAbstract:
Structure and functioning of intertidal food webs along an avian flyway: a comparative approach using stable isotopes
© 2015 British Ecological Society. Food webs and trophic dynamics of coastal systems have been the focus of intense research throughout the world, as they prove to be critical in understanding ecosystem processes and functions. However, very few studies have undertaken a quantitative comparison of entire food webs from a key consumer perspective across a broad geographical area, limiting relevant comparisons among systems with distinct biotic and abiotic components. We investigate the structure and functioning of food webs in four tidal ecosystems of international importance for migratory shorebirds along the East Atlantic Flyway: Tejo estuary in Portugal, Sidi Moussa in Morocco, Banc d'Arguin in Mauritania and Bijagós archipelago in Guinea-Bissau. Basal food sources, shorebirds and their prey (benthic invertebrates) were sampled in all areas, and Bayesian stable isotope mixing models and community-wide metrics were used in a comparative analysis among areas. Significant differences among study areas were found in the structure of food webs, as well as in the relative importance of basal resource pools supporting each food web. Overall, the food web of Banc d'Arguin was characterized by lower trophic diversity and higher functional redundancy than the other sites. This result might be explained by the low number of trophic pathways of organic matter transfer in this seagrass-dominated system which, as a fossil estuary, lacks inputs from both freshwater and nutrient-rich offshore oceanic waters. Structure of shorebird communities was consistent with the main organizational patterns found for each food web, highlighting the less diverse character of the community of Banc d'Arguin. At Banc d'Arguin and Bijagós archipelago, which displayed the smallest and largest isotopic niche widths in bird assemblage, respectively, mean niche overlap among species was low, suggesting high interspecific partitioning in resource use. Tropical systems typically offer comparatively lower harvestable prey biomass for shorebirds and might thus strengthen interspecific competition, leading to low niche overlap among species. Our study reveals relevant differences in the structure of food webs and shorebird communities in coastal areas along an avian flyway. While differences in trophic redundancy of food webs point to distinct levels of ecosystem resilience, contrasts in the organization of shorebird communities highlight the plasticity in the foraging behaviour of species inhabiting areas with distinct environmental conditions.
Abstract.
Silk MJ, Jackson AL, Croft DP, Colhoun K, Bearhop S (2015). The consequences of unidentifiable individuals for the analysis of an animal social network.
Animal Behaviour,
104, 1-11.
Abstract:
The consequences of unidentifiable individuals for the analysis of an animal social network
Social network analysis is pervasive in understanding animal social systems, and provides information about how individuals vary in their social strategies. Many long-term studies comprising uniquely marked individuals use social network analysis as an analytical tool. However, the assumption that it is possible to make inferences using network metrics calculated using a subset of the population has yet to be investigated in an animal social network. We use a simulation study of networks derived from social interactions in a typical fluid fission-fusion social system to determine the precision and accuracy of measures of individual social position based on incomplete knowledge. We show that individual social positions measured in partial social networks correlate strongly with positions in the full social network. This correlation typically becomes stronger as the size of the simulated population is increased and is largely not affected by network density. The choice of network metric has an important effect on the precision of partial networks only when they include a small subset of the population and therefore caution is advised using some of these measures in small partial networks. This work demonstrates that valid inferences about individual social position and strategy can be made using partial networks in a wide range of animal social networks, highlighting the value of applying these methods in large long-term study populations.
Abstract.
Cleasby IR, Wakefield ED, Bearhop S, Bodey TW, Votier SC, Hamer KC (2015). Three-dimensional tracking of a wide-ranging marine predator: flight heights and vulnerability to offshore wind farms.
JOURNAL OF APPLIED ECOLOGY,
52(6), 1474-1482.
Author URL.
Catry T, Lourenço PM, Lopes RJ, Bocher P, Carneiro C, Alves JA, Delaporte P, Bearhop S, Piersma T, Granadeiro JP, et al (2015). Use of stable isotope fingerprints to assign wintering origin and trace shorebird movements along the East Atlantic Flyway.
Basic and Applied EcologyAbstract:
Use of stable isotope fingerprints to assign wintering origin and trace shorebird movements along the East Atlantic Flyway
© 2015 Gesellschaft für Ökologie. Migratory connectivity can be defined as the flux of individuals or populations among areas between stages of an animal's life cycle. Many shorebird species perform long-distance migrations and while moving between breeding and wintering grounds, they depend on a network of intermediate wetlands (stopover sites) where populations of different origins extensively overlap. The difficulty to discriminate such populations represents a serious obstacle to the identification of the links between breeding or wintering areas and stopover sites, and also precludes the estimation of demographic parameters for each population. In this study, we test if linear discriminant models based on stable carbon and nitrogen isotope ratios in toenails can be used to identify populations of several shorebird species of different wintering origins overlapping at two stopover sites of the East Atlantic Flyway. In addition, we evaluate the ability of this approach to infer migratory phenological patterns of shorebirds. Linear discriminant analyses performed overall well in distinguishing the isotopic signals of birds from wintering areas (in France, Portugal, Morocco, Mauritania and Guinea-Bissau) in most species, correctly classifying over 80% (n = 542) of all wintering individuals sampled at these areas. Assignment rates of shorebirds captured during spring migration were also high (96%, n = 323) at the Tejo estuary, Portugal, but lower (40%, n = 185) at Marennes-Oléron Bay in France, and also differed among species. A large proportion of spring migrants captured in Portugal and France were assigned to Banc d'Arguin in Mauritania, the most important wintering area in the flyway. Phenological patterns derived for dunlins (Calidris alpina), common ringed plovers (Charadrius hiaticula) and grey plovers (Pluvialis squatarola) suggest that the first northward migrants started arriving at the Tejo estuary during the second half of March, with peaking numbers occurring during April or May. Migrationskonnektivität kann als die Wechselrate von Individuen oder Populationen in bestimmten Gebieten zwischen zwei Phasen im Lebenszyklus einer Art definiert werden. Viele Watvögel legen weite Strecken zurück, und während des Zuges zwischen Brut- und Überwinterungsgebieten benötigen sie ein Netzwerk von Feuchtgebieten als Rastplätze, wo Populationen unterschiedlicher Herkunft zusammen kommen. Die Schwierigkeit, solche Populationen zu unterscheiden, stellt ein schwerwiegendes Hindernis für die Bestimmung der Verbindungen zwischen Brut- bzw. Überwinterungsgebieten und den Rastplätzen dar und verhindert außerdem die Bestimmung von demographischen Parametern für einzelne Populationen. Wir testeten, ob -basierend auf den Signaturen der stabilen Kohlenstoff- und Stickstoffisotope in Zehennägeln- lineare Diskriminanzmodelle eingesetzt werden können, um die unterschiedlichen Überwinterungsgebiete von Watvögeln zu identifizieren, die an zwei Rastplätzen entlang des Ostatlantischen Zugweges zusammentrafen. Wir bewerteten außerdem die Fähigkeit dieser Methode, Rückschlüsse auf phänologische Muster der ziehenden Watvögel zuzulassen. Die lineare Diskriminanzanalyse bewährte sich für die meisten Arten gut bei der Unterscheidung von Isotopensignaturen der Vögel aus unterschiedlichen Überwinterungsgebieten (Frankreich, Portugal, Marokko, Mauretanien und Guinea-Bissau). Mehr als 80% (n = 542) der in diesen Gebieten untersuchten überwinternden Individuen konnten korrekt eingeordnet werden. Die Zuordnungsraten der Watvögel, die während des Frühjahrszuges im Mündungsgebiet des Tejo gefangen wurden, waren ebenfalls hoch (96%, n = 323), sie waren aber geringer (40%, n = 185) in der Marennes-Oléron-Bucht (Frankreich) und variierten zwischen den Arten. Ein hoher Anteil von Frühjahrsziehern, die in Portugal und Frankreich gefangen wurden, wurde dem Banc d'Arguin-Nationalpark (Mauretanien) zugeordnet, dem wichtigsten Überwinterungsgebiet des Zugweges. Phänologische Muster von Alpenstrandläufer (Calidris alpina), Sandregenpfeifer (Charadrius hiaticula) und Kiebitzregenpfeifer (Pluvialis squatarola) legten nahe, dass die ersten nordwärts ziehenden Vögel während der zweiten Märzhälfte im Mündungsgebiet des Tejo ankamen, wonach die Spitzenwerte im April oder May erreicht wurden.
Abstract.
2014
Perkins MJ, McDonald RA, van Veen FJF, Kelly SD, Rees G, Bearhop S (2014). Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.
PLoS One,
9(3).
Abstract:
Application of nitrogen and carbon stable isotopes (δ(15)N and δ(13)C) to quantify food chain length and trophic structure.
Increasingly, stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C) are used to quantify trophic structure, though relatively few studies have tested accuracy of isotopic structural measures. For laboratory-raised and wild-collected plant-invertebrate food chains spanning four trophic levels we estimated nitrogen range (NR) using δ(15)N, and carbon range (CR) using δ(13)C, which are used to quantify food chain length and breadth of trophic resources respectively. Across a range of known food chain lengths we examined how NR and CR changed within and between food chains. Our isotopic estimates of structure are robust because they were calculated using resampling procedures that propagate variance in sample means through to quantified uncertainty in final estimates. To identify origins of uncertainty in estimates of NR and CR, we additionally examined variation in discrimination (which is change in δ(15)N or δ(13)C from source to consumer) between trophic levels and among food chains. δ(15)N discrimination showed significant enrichment, while variation in enrichment was species and system specific, ranged broadly (1.4‰ to 3.3‰), and importantly, propagated variation to subsequent estimates of NR. However, NR proved robust to such variation and distinguished food chain length well, though some overlap between longer food chains infers a need for awareness of such limitations. δ(13)C discrimination was inconsistent; generally no change or small significant enrichment was observed. Consequently, estimates of CR changed little with increasing food chain length, showing the potential utility of δ(13)C as a tracer of energy pathways. This study serves as a robust test of isotopic quantification of food chain structure, and given global estimates of aquatic food chains approximate four trophic levels while many food chains include invertebrates, our use of four trophic level plant-invertebrate food chains makes our findings relevant for a majority of ecological systems.
Abstract.
Author URL.
Phillips DL, Inger R, Bearhop S, Jackson AL, Moore JW, Parnell AC, Semmens BX, Ward EJ (2014). Best practices for use of stable isotope mixing models in food-web studies.
Canadian Journal of Zoology,
92(10), 823-835.
Abstract:
Best practices for use of stable isotope mixing models in food-web studies
Stable isotope mixing models are increasingly used to quantify consumer diets, but may be misused and misinterpreted. We address major challenges to their effective application. Mixing models have increased rapidly in sophistication. Current models estimate probability distributions of source contributions, have user-friendly interfaces, and incorporate complexities such as variability in isotope signatures, discrimination factors, hierarchical variance structure, covariates, and concentration dependence. For proper implementation of mixing models, we offer the following suggestions. First, mixing models can only be as good as the study and data. Studies should have clear questions, be informed by knowledge of the system, and have strong sampling designs to effectively characterize isotope variability of consumers and resources on proper spatio-temporal scales. Second, studies should use models appropriate for the question and recognize their assumptions and limitations. Decisions about source grouping or incorporation of concentration dependence can influence results. Third, studies should be careful about interpretation of model outputs. Mixing models generally estimate proportions of assimilated resources with substantial uncertainty distributions. Last, common sense, such as graphing data before analyzing, is essential to maximize usefulness of these tools. We hope these suggestions for effective implementation of stable isotope mixing models will aid continued development and application of this field.
Abstract.
Fox AD, Weegman MD, Bearhop S, Hilton GM, Griffin L, Stroud DA, Walsh A (2014). Climate change and contrasting plasticity in timing of a two-step migration episode of an Arctic-nesting avian herbivore.
Current Zoology,
60(2), 233-242.
Abstract:
Climate change and contrasting plasticity in timing of a two-step migration episode of an Arctic-nesting avian herbivore
Greenland white-fronted geese Anser albifrons flavirostris wintering in Britain and Ireland migrate over the sea for 700-1200 km to stage 3-5 weeks in Iceland in spring, continuing a similar distance over the sea and Greenland Ice Cap to West Greenland breeding grounds. During 1969 to 2012, the geese advanced the mean departure date from Ireland by 15 days, during which time also they attained threshold fat stores earlier as well as departing in fatter condition. Over that period, Iceland spring-staging geese shifted from consuming underground plant storage organs to grazing managed hayfields, which provide fresh grass growth despite sub-zero temperatures, when traditional natural foods are inaccessible in frozen substrates. In 2012 and 2013, geese arrived three weeks earlier to Iceland, in fatter condition and accumulated fat significantly slower than in 1997-1999 and 2007. Although geese accumulated sufficient fat stores earlier in Iceland in 2007, 2012 and 2013, they departed around the same date as in 1997-1999, prolonging spring staging by three weeks. Plasticity in winter departure dates is likely due to improved winter feeding conditions (enabling earlier departure in better condition) and a novel predictable food resource in Iceland. Greenland white-fronted geese attained threshold fat stores in Iceland earlier, but remained rather than departing earlier to Greenland. Despite arriving earlier in Iceland, arrival dates on the breeding areas have not changed since the 1880s, presumably because of relatively constant cool springs and heavy snowfall in West Greenland during recent years. © 2014 Current Zoology.
Abstract.
Resano-Mayor J, Hernández-Matías A, Real J, Parés F, Inger R, Bearhop S (2014). Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet.
Ibis,
156(1), 176-188.
Abstract:
Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet
Diet analyses are central to the study of avian trophic ecology, and stable isotope analyses have made an increasing contribution in the last two decades. Few isotopic studies have assessed the diet of raptor species, which are more frequently analysed by conventional diet methods such as pellet analysis. In this study, we compare prey consumption estimates of nestling Bonelli's Eagles Aquila fasciata from conventional pellet analysis (in terms of items and biomass) and stable isotopic mixing models (SIAR) using δ13C, δ15N and δ34S of feathers. The pellet analysis showed that European Rabbits Oryctolagus cuniculus, pigeons (mainly Common Wood Pigeons Columba palumbus and Domestic Pigeons Columba livia dom.), Red-legged Partridges Alectoris rufa, passerines, Yellow-legged Gulls Larus michahellis and Eurasian Red Squirrels Sciurus vulgaris were the main prey, so they were selected for diet reconstructions in SIAR. At the population level, mean prey consumption estimates were similar for pellets (both items and biomass) and SIAR. At the territory level, the weighted kappa statistic showed good ordinal scale agreement in main prey consumption between items or biomass and SIAR. Although the intraclass correlation coefficient showed poor method agreement when considering all prey in the same analysis, the intraclass correlation coefficients for each prey category showed significant agreement between pellets and SIAR when estimating the consumption of Rabbits, pigeons and Gulls, with lower agreement for passerines and Squirrels. Lastly, there was poor method agreement for estimates of Partridges. Our results suggest an overall agreement between the pellet analysis and SIAR when estimating nestling Bonelli's Eagle diet at both the population and, to a lesser extent, the territory level, supporting the usefulness of isotopic mixing models when identifying the terrestrial and marine components of raptor diets. © 2013 British Ornithologists' Union.
Abstract.
O'Farrell S, Bearhop S, Mcgill RAR, Dahlgren CP, Brumbaugh DR, Mumby PJ (2014). Habitat and body size effects on the isotopic niche space of invasive lionfish and endangered Nassau grouper.
ECOSPHERE,
5(10).
Author URL.
Patrick SC, Bearhop S, Gremillet D, Lescroel A, Grecian WJ, Bodey TW, Hamer KC, Wakefield E, Le Nuz M, Votier SC, et al (2014). Individual differences in searching behaviour and spatial foraging consistency in a central place marine predator.
OIKOS,
123(1), 33-40.
Author URL.
Robertson A, McDonald RA, Delahay RJ, Kelly SD, Bearhop S (2014). Individual foraging specialisation in a social mammal: the European badger (Meles meles).
Oecologia,
176(2), 409-421.
Abstract:
Individual foraging specialisation in a social mammal: the European badger (Meles meles).
Individual specialisation has been identified in an increasing number of animal species and populations. However, in some groups, such as terrestrial mammals, it is difficult to disentangle individual niche variation from spatial variation in resource availability. In the present study, we investigate individual variation in the foraging niche of the European badger (Meles meles), a social carnivore that lives in a shared group territory, but forages predominantly alone. Using stable isotope analysis, we distinguish the extent to which foraging variation in badgers is determined by social and spatial constraints and by individual differences within groups. We found a tendency for individual badgers within groups to differ markedly and consistently in their isotope values, suggesting that individuals living with access to the same resources occupied distinctive foraging niches. Although sex had a significant effect on isotope values, substantial variation within groups occurred independently of age and sex. Individual differences were consistent over a period of several months and in some instances were highly consistent across the two years of the study, suggesting long-term individual foraging specialisations. Individual specialisation in foraging may, therefore, persist in populations of territorial species not solely as a result of spatial variation in resources, but also arising from individuals selecting differently from the same available resources. Although the exact cause of this behaviour is unknown, we suggest that specialisation may occur due to learning trade-offs which may limit individual niche widths. However, ecological factors at the group level, such as competition, may also influence the degree of specialisation.
Abstract.
Author URL.
Saporiti F, Bearhop S, Silva L, Vales DG, Zenteno L, Crespo EA, Aguilar A, Cardona L (2014). Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past.
PLoS One,
9(7).
Abstract:
Longer and less overlapping food webs in anthropogenically disturbed marine ecosystems: confirmations from the past.
The human exploitation of marine resources is characterised by the preferential removal of the largest species. Although this is expected to modify the structure of food webs, we have a relatively poor understanding of the potential consequences of such alteration. Here, we take advantage of a collection of ancient consumer tissues, using stable isotope analysis and SIBER to assess changes in the structure of coastal marine food webs in the South-western Atlantic through the second half of the Holocene as a result of the sequential exploitation of marine resources by hunter-gatherers, western sealers and modern fishermen. Samples were collected from shell middens and museums. Shells of both modern and archaeological intertidal herbivorous molluscs were used to reconstruct changes in the stable isotopic baseline, while modern and archaeological bones of the South American sea lion Otaria flavescens, South American fur seal Arctocephalus australis and Magellanic penguin Spheniscus magellanicus were used to analyse changes in the structure of the community of top predators. We found that ancient food webs were shorter, more redundant and more overlapping than current ones, both in northern-central Patagonia and southern Patagonia. These surprising results may be best explained by the huge impact of western sealing on pinnipeds during the fur trade period, rather than the impact of fishing on fish populations. As a consequence, the populations of pinnipeds at the end of the sealing period were likely well below the ecosystem's carrying capacity, which resulted in a release of intraspecific competition and a shift towards larger and higher trophic level prey. This in turn led to longer and less overlapping food webs.
Abstract.
Author URL.
Resano-Mayor J, Hernández-Matías A, Real J, Moleón M, Parés F, Inger R, Bearhop S (2014). Multi-scale effects of nestling diet on breeding performance in a terrestrial top predator inferred from stable isotope analysis.
PLoS One,
9(4).
Abstract:
Multi-scale effects of nestling diet on breeding performance in a terrestrial top predator inferred from stable isotope analysis.
Inter-individual diet variation within populations is likely to have important ecological and evolutionary implications. The diet-fitness relationships at the individual level and the emerging population processes are, however, poorly understood for most avian predators inhabiting complex terrestrial ecosystems. In this study, we use an isotopic approach to assess the trophic ecology of nestlings in a long-lived raptor, the Bonelli's eagle Aquila fasciata, and investigate whether nestling dietary breath and main prey consumption can affect the species' reproductive performance at two spatial scales: territories within populations and populations over a large geographic area. At the territory level, those breeding pairs whose nestlings consumed similar diets to the overall population (i.e. moderate consumption of preferred prey, but complemented by alternative prey categories) or those disproportionally consuming preferred prey were more likely to fledge two chicks. An increase in the diet diversity, however, related negatively with productivity. The age and replacements of breeding pair members had also an influence on productivity, with more fledglings associated to adult pairs with few replacements, as expected in long-lived species. At the population level, mean productivity was higher in those population-years with lower dietary breadth and higher diet similarity among territories, which was related to an overall higher consumption of preferred prey. Thus, we revealed a correspondence in diet-fitness relationships at two spatial scales: territories and populations. We suggest that stable isotope analyses may be a powerful tool to monitor the diet of terrestrial avian predators on large spatio-temporal scales, which could serve to detect potential changes in the availability of those prey on which predators depend for breeding. We encourage ecologists and evolutionary and conservation biologists concerned with the multi-scale fitness consequences of inter-individual variation in resource use to employ similar stable isotope-based approaches, which can be successfully applied to complex ecosystems such as the Mediterranean.
Abstract.
Author URL.
Maclean IM, Inger R, Booth CG, Embling CB, Grecian WJ, Heymans JJ, Plummer K, Shackshaft M, Sparling C, Wilson B, et al (2014). Resolving issues with environmental impact assessment of marine renewable energy installations. Frontiers in Marine Science, 1(75).
Bodey TW, Jessopp MJ, Votier SC, Gerritsen HD, Cleasby IR, Hamer KC, Patrick SC, Wakefield ED, Bearhop S (2014). Seabird movement reveals the ecological footprint of fishing vessels.
Curr Biol,
24(11), R514-R515.
Abstract:
Seabird movement reveals the ecological footprint of fishing vessels.
Exploitation of the seas is currently unsustainable, with increasing demand for marine resources placing intense pressure on the Earth's largest ecosystem [1]. The scale of anthropogenic effects varies from local to entire ocean basins [1-3]. For example, discards of commercial capture fisheries can have both positive and negative impacts on scavengers at the population and community-level [2-6], although this is driven by individual foraging behaviour [3,7]. Currently, we have little understanding of the scale at which individual animals initiate such behaviours. We use the known interaction between fisheries and a wide-ranging seabird, the Northern gannet Morus bassanus[3], to investigate how fishing vessels affect individual birds' behaviours in near real-time. We document the footprint of fishing vessels' (≥15 m length) influence on foraging decisions (≤11 km), and a potential underlying behavioural mechanism, by revealing how birds respond differently to vessels depending on gear type and activity. Such influences have important implications for fisheries, including the proposed discard ban [8]), and wider marine management.
Abstract.
Author URL.
Bodey TW, Ward EJ, Phillips RA, McGill RAR, Bearhop S (2014). Species versus guild level differentiation revealed across the annual cycle by isotopic niche examination.
Journal of Animal Ecology,
83(2), 470-478.
Abstract:
Species versus guild level differentiation revealed across the annual cycle by isotopic niche examination
Interspecific competitive interactions typically result in niche differentiation to alleviate competition through mechanisms including character displacement. However, competition is not the sole constraint on resource partitioning, and its effects are mediated by factors including the environmental context in which species coexist. Colonial seabirds provide an excellent opportunity to investigate the importance of competition in shaping realized niche widths because their life histories lead to variation in intra- and interspecific competition across the annual cycle. Dense breeding aggregations result in intense competition for prey in surrounding waters, whereas non-breeding dispersal to larger geographical areas produces lower densities of competitors. Bayesian hierarchical models of the isotopic niche, closely aligned to the trophic niche, reveal the degree of segregation between species and functional groups during both time periods. Surprisingly, species explained far more of the variance in the isotopic niche during the non-breeding than the breeding period. Our results underline the key role of non-breeding dynamics in alleviating competition and promoting distinctions between species through the facilitation of resource partitioning. Such situations may be common in a diverse range of communities sustained by ephemeral but abundant food items. This highlights how consideration of the hierarchical grouping of competitive interactions alongside consideration of abiotic constraints across the complete annual cycle allows a full understanding of the role of competition in driving patterns of character displacement. © 2013 the Authors. Journal of Animal Ecology © 2013 British Ecological Society.
Abstract.
Bodey TW, Ward EJ, Phillips RA, McGill RAR, Bearhop S (2014). Species versus guild level differentiation revealed across the annual cycle by isotopic niche examination.
J Anim Ecol,
83(2), 470-478.
Abstract:
Species versus guild level differentiation revealed across the annual cycle by isotopic niche examination.
Interspecific competitive interactions typically result in niche differentiation to alleviate competition through mechanisms including character displacement. However, competition is not the sole constraint on resource partitioning, and its effects are mediated by factors including the environmental context in which species coexist. Colonial seabirds provide an excellent opportunity to investigate the importance of competition in shaping realized niche widths because their life histories lead to variation in intra- and interspecific competition across the annual cycle. Dense breeding aggregations result in intense competition for prey in surrounding waters, whereas non-breeding dispersal to larger geographical areas produces lower densities of competitors. Bayesian hierarchical models of the isotopic niche, closely aligned to the trophic niche, reveal the degree of segregation between species and functional groups during both time periods. Surprisingly, species explained far more of the variance in the isotopic niche during the non-breeding than the breeding period. Our results underline the key role of non-breeding dynamics in alleviating competition and promoting distinctions between species through the facilitation of resource partitioning. Such situations may be common in a diverse range of communities sustained by ephemeral but abundant food items. This highlights how consideration of the hierarchical grouping of competitive interactions alongside consideration of abiotic constraints across the complete annual cycle allows a full understanding of the role of competition in driving patterns of character displacement.
Abstract.
Author URL.
Fox AD, Walsh AJ, Weegman MD, Bearhop S, Mitchell C (2014). Spring ice formation on goose neck collars: effects on body condition and survival in Greenland white-fronted geese Anser albifrons flavirostris.
EUROPEAN JOURNAL OF WILDLIFE RESEARCH,
60(5), 831-834.
Author URL.
Savidge G, Ainsworth D, Bearhop S, Christen N, Elsaesser B, Fortune F, Inger R, Kennedy R, McRobert A, Plummer KE, et al (2014). Strangford Lough and the SeaGen Tidal Turbine. In (Ed) Marine Renewable Energy Technology and Environmental Interactions, 153-172.
Silk MJ, Croft DP, Tregenza T, Bearhop S (2014). The importance of fission-fusion social group dynamics in birds.
IBIS,
156(4), 701-715.
Author URL.
Gavrilchuk K, Lesage V, Ramp C, Sears R, Bérubé M, Bearhop S, Beauplet G (2014). Trophic niche partitioning among sympatric baleen whale species following the collapse of groundfish stocks in the Northwest Atlantic.
Marine Ecology Progress Series,
497, 285-301.
Abstract:
Trophic niche partitioning among sympatric baleen whale species following the collapse of groundfish stocks in the Northwest Atlantic
Ecologically similar species may coexist when resource partitioning over time and space reduces interspecific competition. Understanding resource use within these species assemblages may help predict how species relative abundance might influence ecosystem functioning. In the Gulf of St. Lawrence, Canada, 4 species of rorqual whales (blue Balaenoptera musculus, fin B. physalus, minke B. acutorostrata and humpback Megaptera novaeangliae) coexist during the summer feeding period. They can be observed within hundreds of meters of one another, suggesting an overlap in ecological niches; yet fine-scale habitat use analyses suggest some resource partitioning. While major ecological changes have been observed in marine ecosystems, including the Gulf of St. Lawrence, we have little understanding of how the removal of predatory fish might cascade through ecosystems. Here, we take advantage of a 19 yr tissue collection subsequent to a fishery collapse (which occurred in 1992) to investigate trophic niche partitioning within a guild of rorqual whales following the loss of a key ecosystem component, groundfish. We analyzed stable isotope ratios for 626 rorqual individuals sampled between 1992 and 2010. Using Bayesian isotopic mixing models, we demonstrated that the 4 rorqual species segregated trophically by consuming different proportions of shared prey. An overall increase in δ15N values over the study period (post groundfish collapse), particularly for fin and humpback whales, suggested a progressive use of higher-trophic level prey, such as small pelagic fish, whereas the stability of blue whale diet over time confirmed their specialized feeding behaviour. This study provides the first longterm assessment of trophic ecology among rorqual populations on this Northwest Atlantic feeding ground, and evidence for differential resource use among large marine predators following ecosystem change. © 2014 Inter-Research.
Abstract.
2013
Weber NL, Carter SP, Dall SRX, Delahay RJ, McDonald JL, Bearhop S, McDonald RA (2013). Badger social networks correlate with tuberculosis infection.
Current Biology,
23(20), R915-R916.
Abstract:
Badger social networks correlate with tuberculosis infection
Although disease hosts are classically assumed to interact randomly, infection is likely to spread across structured and dynamic contact networks. We used social network analyses to investigate contact patterns of group-living European badgers Meles meles, which are an important wildlife reservoir of bovine tuberculosis (TB). We found that TB test-positive badgers were socially isolated from their own groups but were more important for flow, potentially of infection, between social groups. The distinctive social position of infected badgers may help explain how social stability mitigates, and social perturbation increases, the spread of infection in badgers.
Abstract.
Parnell AC, Phillips DL, Bearhop S, Semmens BX, Ward EJ, Moore JW, Jackson AL, Grey J, Kelly DJ, Inger R, et al (2013). Bayesian stable isotope mixing models.
Environmetrics,
24(6), 387-399.
Abstract:
Bayesian stable isotope mixing models
In this paper, we review recent advances in stable isotope mixing models (SIMMs) and place them into an overarching Bayesian statistical framework, which allows for several useful extensions. SIMMs are used to quantify the proportional contributions of various sources to a mixture. The most widely used application is quantifying the diet of organisms based on the food sources they have been observed to consume. At the centre of the multivariate statistical model we propose is a compositional mixture of the food sources corrected for various metabolic factors. The compositional component of our model is based on the isometric log-ratio transform. Through this transform, we can apply a range of time series and non-parametric smoothing relationships. We illustrate our models with three case studies based on real animal dietary behaviour. © 2013 John Wiley & Sons, Ltd.
Abstract.
Resano-Mayor J, Hernández-Matías A, Real J, Parés F, Inger R, Bearhop S (2013). Comparing pellet and stable isotope analyses of nestling Bonelli's Eagle Aquila fasciata diet. Ibis
Weber N, Bearhop S, Dall SRX, Delahay RJ, McDonald RA, Carter SP (2013). Denning behaviour of the European badger (Meles meles) correlates with bovine tuberculosis infection status.
Behavioral Ecology and Sociobiology,
67, 471-479.
Abstract:
Denning behaviour of the European badger (Meles meles) correlates with bovine tuberculosis infection status
Heterogeneities in behaviours of individuals may underpin important processes in evolutionary biology and ecology, including the spread of disease. Modelling approaches can sometimes fail to predict disease spread, which may partly be due to the number of unknown sources of variation in host behaviour. The European badger is a wildlife reservoir for bovine tuberculosis (bTB) in Britain and Ireland, and individual behaviour has been demonstrated to be an important factor in the spread of bTB among badgers and to cattle. Radio-telemetry devices were deployed on 40 badgers from eight groups to investigate patterns of den (sett) use in a high-density population, where each group had one or two main and three to eight outlier setts in their territory. Badgers were located at their setts for 28 days per season for one year to investigate how patterns differed between individuals. Denning behaviour may have a strong influence on contact patterns and the transmission of disease. We found significant heterogeneity, influenced by season, sex and age. Also, when controlling for these, bTB infection status interacting with season was highly correlated with sett use. Test-positive badgers spent more time away from their main sett than those that tested negative. We speculate that wider-ranging behaviour of test-positive animals may result in them contacting sources of infection more frequently and/or that their behaviour may be influenced by their disease status. Measures to control infectious diseases might be improved by targeting functional groups, specific areas, or times of year that may contribute disproportionately to disease spread.
Abstract.
Harrison XA, Hodgson DJ, Inger R, Colhoun K, Gudmundsson GA, McElwaine G, Tregenza T, Bearhop S (2013). Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
PLoS One,
8(10).
Abstract:
Environmental conditions during breeding modify the strength of mass-dependent carry-over effects in a migratory bird.
In many animals, processes occurring in one season carry over to influence reproductive success and survival in future seasons. The strength of such carry-over effects is unlikely to be uniform across years, yet our understanding of the processes that are capable of modifying their strength remains limited. Here we show that female light-bellied Brent geese with higher body mass prior to spring migration successfully reared more offspring during breeding, but only in years where environmental conditions during breeding were favourable. In years of bad weather during breeding, all birds suffered reduced reproductive output irrespective of pre-migration mass. Our results suggest that the magnitude of reproductive benefits gained by maximising body stores to fuel breeding fluctuates markedly among years in concert with conditions during the breeding season, as does the degree to which carry-over effects are capable of driving variance in reproductive success among individuals. Therefore while carry-over effects have considerable power to drive fitness asymmetries among individuals, our ability to interpret these effects in terms of their implications for population dynamics is dependent on knowledge of fitness determinants occurring in subsequent seasons.
Abstract.
Author URL.
Plummer KE, Bearhop S, Leech DI, Chamberlain DE, Blount JD (2013). Fat provisioning in winter impairs egg production during the following spring: a landscape-scale study of blue tits.
Journal of Animal Ecology,
82(3), 673-682.
Abstract:
Fat provisioning in winter impairs egg production during the following spring: a landscape-scale study of blue tits
Summary: Provisioning of garden birds is a growing phenomenon, particularly during winter, but there is little empirical evidence of its true ecological impacts. One possibility is that winter provisioning could enhance subsequent breeding performance, but this seems likely to depend on the types of nutrients provided. For example, whereas effects of macronutrients such as fat are unlikely to be carried over to influence breeding in small passerines, micronutrients such as dietary vitamin E (an antioxidant) may be stored or have lasting health benefits. Here, we examine the carry-over effects of winter food supplements on egg production in wild populations of blue tits (Cyanistes caeruleus). Over three consecutive years, birds were provisioned with fat, fat plus vitamin E or remained unfed (controls). The provision of fat in winter resulted in smaller relative yolk mass in larger eggs and reduced yolk carotenoid concentrations in early breeders. However, these effects were not seen in birds provisioned with fat plus vitamin E. Lay date, clutch size, egg mass and yolk vitamin E concentrations were not significantly affected by winter provisioning treatment. Our results indicate that winter provisioning can have important downstream consequences, in particular affecting investment in egg production several weeks or months later. Provisioning is widely applied to support garden bird populations and for the conservation management of endangered species. However, our results challenge the assumption that such practices are always beneficial at the population level and emphasize how the ecological impacts can depend on the specific nutritional profile of provisioned foods. © 2013 British Ecological Society.
Abstract.
Plummer KE, Bearhop S, Leech DI, Chamberlain DE, Blount JD (2013). Fat provisioning in winter impairs egg production during the following spring: a landscape-scale study of blue tits.
J Anim Ecol,
82(3), 673-682.
Abstract:
Fat provisioning in winter impairs egg production during the following spring: a landscape-scale study of blue tits.
1. Provisioning of garden birds is a growing phenomenon, particularly during winter, but there is little empirical evidence of its true ecological impacts. One possibility is that winter provisioning could enhance subsequent breeding performance, but this seems likely to depend on the types of nutrients provided. For example, whereas effects of macronutrients such as fat are unlikely to be carried over to influence breeding in small passerines, micronutrients such as dietary vitamin E (an antioxidant) may be stored or have lasting health benefits. 2. Here, we examine the carry-over effects of winter food supplements on egg production in wild populations of blue tits (Cyanistes caeruleus). Over three consecutive years, birds were provisioned with fat, fat plus vitamin E or remained unfed (controls). 3. The provision of fat in winter resulted in smaller relative yolk mass in larger eggs and reduced yolk carotenoid concentrations in early breeders. However, these effects were not seen in birds provisioned with fat plus vitamin E. Lay date, clutch size, egg mass and yolk vitamin E concentrations were not significantly affected by winter provisioning treatment. 4. Our results indicate that winter provisioning can have important downstream consequences, in particular affecting investment in egg production several weeks or months later. 5. Provisioning is widely applied to support garden bird populations and for the conservation management of endangered species. However, our results challenge the assumption that such practices are always beneficial at the population level and emphasize how the ecological impacts can depend on the specific nutritional profile of provisioned foods.
Abstract.
Author URL.
Perkins MJ, Mcdonald RA, van Veen FJF, Kelly SD, Rees G, Bearhop S (2013). Important impacts of tissue selection and lipid extraction on ecological parameters derived from stable isotope ratios.
Methods in Ecology and Evolution,
4(10), 944-953.
Abstract:
Important impacts of tissue selection and lipid extraction on ecological parameters derived from stable isotope ratios
Summary: the nitrogen (δ15N) and carbon (δ13C) isotope ratios of animal tissues can help identify the composition of diets and open up a myriad of ecological applications. However, consumers do not ingest or assimilate all components of food items, and it is not well understood how sampling different tissues of sources and consumers may affect isotopic values ascribed, and thereby how such variation affects derived ecological measures. Utilizing a simple prey-predator feeding relationship in insects, we examined isotopic differences in soft, exoskeleton and whole tissues using samples with and without lipid extraction. As a derived ecological measure, we calculated trophic discrimination factors, changes in δ15N or δ13C between source and consumer, for the different prey-predator tissue combinations. Lipid extraction did not affect δ15N values, and we found significant tissue differences in δ15N that varied between prey and predator. Lipid extraction enriched δ13C values in most instances, and it was only after extraction of lipids that we observed consistent depletion of δ13C in exoskeleton relative to soft tissues in prey and predator. Isotopic differences between tissue types propagated marked variation in derived ecological parameters. Common sampling practice using whole tissue for prey and predator (whole/whole) resulted in a trophic discrimination factor of 0·48‰ for δ15N, compared with correct factors of 0·97‰ (soft/whole) and 2·18‰ (soft/soft) using prey soft tissue actually ingested by the predator. For δ13C, variation across discrimination factors was less, with whole/whole tissue of -0·14‰, whilst correct factors were -0·55‰ (soft/whole) and -0·04‰ (soft/soft). Our results indicate that tissue selection and preparation are important considerations for isotopic studies using arthropods. Lipid extraction is necessary to derive accurate δ13C values based on proteins, whilst consequences of tissue selection are likely context-dependent: in poorly defined systems where sources are isotopically similar or have larger variance, our results indicate that tissue selection within sources is important to avoid significant error, whether estimating trophic positions or dietary proportions using mixing models. In such cases, we strongly recommend exclusion of source materials not assimilated in consumers. © 2013 British Ecological Society.
Abstract.
Moussy C, Hosken DJ, Mathews F, Smith GC, Aegerter JN, Bearhop S (2013). Migration and dispersal patterns of bats and their influence on genetic structure. Mammal Review, 43, 183-195.
Dwyer RG, Bearhop S, Campbell HA, Bryant DM (2013). Shedding light on light: Benefits of anthropogenic illumination to a nocturnally foraging shorebird.
Journal of Animal Ecology,
82(2), 478-485.
Abstract:
Shedding light on light: Benefits of anthropogenic illumination to a nocturnally foraging shorebird
Intertidal habitats provide important feeding areas for migratory shorebirds. Anthropogenic developments along coasts can increase ambient light levels at night across adjacent inter-tidal zones. Here, we report the effects of elevated nocturnal light levels upon the foraging strategy of a migratory shorebird (common redshank Tringa totanus) overwintering on an industrialised estuary in Northern Europe. To monitor behaviour across the full intertidal area, individuals were located by day and night using VHF transmitters, and foraging behaviour was inferred from inbuilt posture sensors. Natural light was scored using moon-phase and cloud cover information and nocturnal artificial light levels were obtained using geo-referenced DMSP/OLS night-time satellite imagery at a 1-km resolution. Under high illumination levels, the commonest and apparently preferred foraging behaviour was sight-based. Conversely, birds feeding in areas with low levels of artificial light had an elevated foraging time and fed by touch, but switched to visual rather than tactile foraging behaviour on bright moonlit nights in the absence of cloud cover. Individuals occupying areas which were illuminated continuously by lighting from a large petrochemical complex invariably exhibited a visually based foraging behaviour independently of lunar phase and cloud cover. We show that ambient light levels affect the timing and distribution of foraging opportunities for redshank. We argue that light emitted from an industrial complex improved nocturnal visibility. This allowed sight-based foraging in place of tactile foraging, implying both a preference for sight-feeding and enhanced night-time foraging opportunities under these conditions. The study highlights the value of integrating remotely sensed data and telemetry techniques to assess the effect of anthropogenic change upon nocturnal behaviour and habitat use. © 2012 the Authors. Journal of Animal Ecology © 2012 British Ecological Society.
Abstract.
Dwyer RG, Bearhop S, Campbell HA, Bryant DM (2013). Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird.
J Anim Ecol,
82(2), 478-485.
Abstract:
Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird.
Intertidal habitats provide important feeding areas for migratory shorebirds. Anthropogenic developments along coasts can increase ambient light levels at night across adjacent inter-tidal zones. Here, we report the effects of elevated nocturnal light levels upon the foraging strategy of a migratory shorebird (common redshank Tringa totanus) overwintering on an industrialised estuary in Northern Europe. To monitor behaviour across the full intertidal area, individuals were located by day and night using VHF transmitters, and foraging behaviour was inferred from inbuilt posture sensors. Natural light was scored using moon-phase and cloud cover information and nocturnal artificial light levels were obtained using geo-referenced DMSP/OLS night-time satellite imagery at a 1-km resolution. Under high illumination levels, the commonest and apparently preferred foraging behaviour was sight-based. Conversely, birds feeding in areas with low levels of artificial light had an elevated foraging time and fed by touch, but switched to visual rather than tactile foraging behaviour on bright moonlit nights in the absence of cloud cover. Individuals occupying areas which were illuminated continuously by lighting from a large petrochemical complex invariably exhibited a visually based foraging behaviour independently of lunar phase and cloud cover. We show that ambient light levels affect the timing and distribution of foraging opportunities for redshank. We argue that light emitted from an industrial complex improved nocturnal visibility. This allowed sight-based foraging in place of tactile foraging, implying both a preference for sight-feeding and enhanced night-time foraging opportunities under these conditions. The study highlights the value of integrating remotely sensed data and telemetry techniques to assess the effect of anthropogenic change upon nocturnal behaviour and habitat use.
Abstract.
Author URL.
Wakefield ED, Bodey TW, Bearhop S, Blackburn J, Colhoun K, Davies R, Dwyer RG, Green JA, Gremillet D, Jackson AL, et al (2013). Space Partitioning Without Territoriality in Gannets.
SCIENCE,
341(6141), 68-70.
Author URL.
Wakefield ED, Bodey TW, Bearhop S, Blackburn J, Colhoun K, Davies R, Dwyer RG, Green JA, Grémillet D, Jackson AL, et al (2013). Space partitioning without territoriality in gannets.
Science,
341(6141), 68-70.
Abstract:
Space partitioning without territoriality in gannets
Colonial breeding is widespread among animals. Some, such as eusocial insects, may use agonistic behavior to partition available foraging habitat into mutually exclusive territories; others, such as breeding seabirds, do not. We found that northern gannets, satellite-tracked from 12 neighboring colonies, nonetheless forage in largely mutually exclusive areas and that these colony-specific home ranges are determined by density-dependent competition. This segregation may be enhanced by individual-level public information transfer, leading to cultural evolution and divergence among colonies.
Abstract.
Semmens BX, Ward EJ, Parnell AC, Phillips DL, Bearhop S, Inger R, Jackson A, Moore JW (2013). Statistical basis and outputs of stable isotope mixing models: Comment on Fry (2013).
Marine Ecology Progress Series,
490, 285-289.
Abstract:
Statistical basis and outputs of stable isotope mixing models: Comment on Fry (2013)
Fry (2013; Mar Ecol Prog Ser 472:1-13) reviewed approaches to solving under - determined stable isotope mixing systems, and presented a novel approach based on graphi - cal summaries. He inaccurately characterized the statistics and interpretation of outputs from IsoSource and more recent Bayesian mixing model tools (e.g. SIAR, MixSIR), however, and as an alternative promoted an approach-not based on likelihood methods-that uses graphing and 2 new metrics for tracking source contributions to a mixture. Fry's approach does not provide statistical probability densities associated with source contribution parameter estimates, has little applicability to complex mixing systems such as hierarchical models, and relies on the subjective interpretation of graphing products. We clarify the analytic theory underlying common mixing model approaches and provide an analysis of the 4-source, 2-tracer underdetermined mixing system example in Fry (2013), using both a Bayesian mixing model and Fry's graphical analysis and summary metrics. We demonstrate that properly interpreted Bayesian approaches yield distributions of parameter estimates that can reflect multi-modality, covariance and parameter uncertainty. © Inter-Research 2013.
Abstract.
Fuller RA, Bearhop S, Metcalfe NB, Piersma T (2013). The effect of group size on vigilance in Ruddy Turnstones Arenaria interpres varies with foraging habitat.
Ibis,
155(2), 246-257.
Abstract:
The effect of group size on vigilance in Ruddy Turnstones Arenaria interpres varies with foraging habitat
Foraging birds can manage time spent vigilant for predators by forming groups of various sizes. However, group size alone will not always reliably determine the optimal level of vigilance. For example, variation in predation risk or food quality between patches may also be influential. In a field setting, we assessed how simultaneous variation in predation risk and intake rate affects the relationship between vigilance and group size in foraging Ruddy Turnstones Arenaria interpres. We compared vigilance, measured as the number of 'head-ups' per unit time, in habitat types that differed greatly in prey energy content and proximity to cover from which predators could launch surprise attacks. Habitats closer to predator cover provided foragers with much higher potential net energy intake rates than habitats further from cover. Foragers formed larger and denser flocks on habitats closer to cover. Individual vigilance of foragers in all habitats declined with increasing flock size and increased with flock density. However, vigilance by foragers on habitats closer to cover was always higher for a given flock size than vigilance by foragers on habitats further from cover, and habitat remained an important predictor of vigilance in models including a range of potential confounding variables. Our results suggest that foraging Ruddy Turnstones can simultaneously assess information on group size and the general likelihood of predator attack when determining their vigilance contribution. © 2012 British Ornithologists' Union.
Abstract.
Plummer KE, Bearhop S, Leech DI, Chamberlain DE, Blount JD (2013). Winter food provisioning reduces future breeding performance in a wild bird.
Sci Rep,
3Abstract:
Winter food provisioning reduces future breeding performance in a wild bird.
Supplementation of food to wild birds occurs on an enormous scale worldwide, and is often cited as an exemplar of beneficial human-wildlife interaction. Recently it has been speculated that winter feeding could have negative consequences for future reproduction, for example by enabling low quality individuals to recruit into breeding populations. However, evidence that winter feeding has deleterious impacts on reproductive success is lacking. Here, in a landscape-scale study of blue tits (Cyanistes caeruleus) across multiple years, we show that winter food supplementation reduced breeding performance the following spring. Compared to unfed populations, winter-fed birds produced offspring that weighed less, were smaller, and had lower survival. This impairment was observed in parents that had received fat only, or in combination with vitamin E, suggesting some generality in the mechanism by which supplementary feeding affected reproduction. Our results highlight the potential for deleterious population-level consequences of winter food supplementation on wild birds.
Abstract.
Author URL.
2012
Grecian WJ, Witt MJ, Attrill MJ, Bearhop S, Godley BJ, Grémillet D, Hamer KC, Votier SC (2012). A novel projection technique to identify important at-sea areas for seabird conservation: an example using Northern gannets breeding in the North East Atlantic. Biological Conservation
Grecian WJ, Witt MJ, Attrill MJ, Bearhop S, Godley BJ, Grémillet D, Hamer KC, Votier SC (2012). A novel projection technique to identify important at-sea areas for seabird conservation: an example using Northern gannets breeding in the North East Atlantic.
Biological Conservation,
156, 43-52.
Abstract:
A novel projection technique to identify important at-sea areas for seabird conservation: an example using Northern gannets breeding in the North East Atlantic
Seabirds are well monitored and protected at their breeding grounds but spend most of their life at sea, where they are less well monitored and afforded little protection. In an attempt to address this dichotomy, attention has been directed toward establishing a network of marine reserves for seabirds, based largely on information from at-sea surveys and/or biotelemetry studies. Nevertheless, these approaches are costly, are typically only available for a limited number of locations, and not suitable for species that have either poor at-sea detectability or are unable to carry tracking devices. Here we develop a technique to identify important areas for breeding seabirds based on at-sea projections from colonies. Synthesising data from colony surveys with detailed information on population dynamics, foraging ecology and near-colony behaviour, we project colony-specific foraging distributions of the Northern gannet (. Morus bassanus) at colonies in the UK, Ireland and France. We test the ability of our models to identify at-sea hotspots through comparison with existing data from biotelemetry studies and at-sea visual surveys. These models show a positive spatial correlation with one of the most intensive at-sea seabird survey datasets. While there are limitations to estimating at-sea distributions of seabirds, implemented appropriately, we propose they could prove useful in identifying potential Marine Protected Areas for seabirds. Moreover, these models could be developed to suit a range of species or whole communities and provide a theoretical framework for the study of factors such as colony size regulation. © 2012 Elsevier Ltd.
Abstract.
Brown SL, Bearhop S, Harrod C, McDonald RA (2012). A review of spatial and temporal variation in grey and common seal diet in the United Kingdom and Ireland.
Journal of the Marine Biological Association of the United Kingdom,
92(8), 1711-1722.
Abstract:
A review of spatial and temporal variation in grey and common seal diet in the United Kingdom and Ireland
Knowledge about the diet of fish-eating predators is critical when evaluating conflicts with the fishing industry. Numerous primary studies have examined the diet of grey seals Halichoerus grypus and common seals Phoca vitulina in a bid to understand the ecology of these predators. However, studies of large-scale spatial and temporal variation in seal diet are limited. Therefore this review combines the results of seal diet studies published between 1980 and 2000 to examine how seal diet varies at a range of spatial and temporal scales. Our results revealed extensive spatial variation in gadiform, perciform and flatfish consumption, likely reflecting variation in prey availability. Flatfish and gadiform consumption varied between years, reflecting changes in fish assemblages as a consequence of factors such as varying fishing pressures, climate change and natural fluctuations in populations. Perciform and gadiform consumption varied seasonally: in addition there was a significant interaction between season and seal species, indicating that grey and common seals exhibited different patterns of seasonal variation in their consumption of Perciformes and Gadiformes. Multivariate analysis of grey seal diet revealed spatial variation at a much smaller scale, with different species dominating the diet in different areas. The existence of spatial and temporal variation in seal diet emphasizes that future assessments of the impact of seal populations should not be based on past or localized estimates of diet and highlights the need for up-to-date, site specific estimates of diet composition in the context of understanding and resolving seal/fisheries conflict. © 2012 Marine Biological Association of the United Kingdom.
Abstract.
Layman CA, Araujo MS, Boucek R, Hammerschlag-Peyer CM, Harrison E, Jud ZR, Matich P, Rosenblatt AE, Vaudo JJ, Yeager LA, et al (2012). Applying stable isotopes to examine food-web structure: an overview of analytical tools.
Biological Reviews,
87(3), 545-562.
Abstract:
Applying stable isotopes to examine food-web structure: an overview of analytical tools
Stable isotope analysis has emerged as one of the primary means for examining the structure and dynamics of food webs, and numerous analytical approaches are now commonly used in the field. Techniques range from simple, qualitative inferences based on the isotopic niche, to Bayesian mixing models that can be used to characterize food-web structure at multiple hierarchical levels. We provide a comprehensive review of these techniques, and thus a single reference source to help identify the most useful approaches to apply to a given data set. We structure the review around four general questions: (1) what is the trophic position of an organism in a food web?; (2) which resource pools support consumers?; (3) what additional information does relative position of consumers in isotopic space reveal about food-web structure?; and (4) what is the degree of trophic variability at the intrapopulation level? for each general question, we detail different approaches that have been applied, discussing the strengths and weaknesses of each. We conclude with a set of suggestions that transcend individual analytical approaches, and provide guidance for future applications in the field. © 2011 the Authors. Biological Reviews © 2011 Cambridge Philosophical Society.
Abstract.
Layman CA, Araujo MS, Boucek R, Hammerschlag-Peyer CM, Harrison E, Jud ZR, Matich P, Rosenblatt AE, Vaudo JJ, Yeager LA, et al (2012). Applying stable isotopes to examine food-web structure: an overview of analytical tools.
Biol Rev Camb Philos Soc,
87(3), 545-562.
Abstract:
Applying stable isotopes to examine food-web structure: an overview of analytical tools.
Stable isotope analysis has emerged as one of the primary means for examining the structure and dynamics of food webs, and numerous analytical approaches are now commonly used in the field. Techniques range from simple, qualitative inferences based on the isotopic niche, to Bayesian mixing models that can be used to characterize food-web structure at multiple hierarchical levels. We provide a comprehensive review of these techniques, and thus a single reference source to help identify the most useful approaches to apply to a given data set. We structure the review around four general questions: (1) what is the trophic position of an organism in a food web?; (2) which resource pools support consumers?; (3) what additional information does relative position of consumers in isotopic space reveal about food-web structure?; and (4) what is the degree of trophic variability at the intrapopulation level? for each general question, we detail different approaches that have been applied, discussing the strengths and weaknesses of each. We conclude with a set of suggestions that transcend individual analytical approaches, and provide guidance for future applications in the field.
Abstract.
Author URL.
Witt MJ, Sheehan EV, Bearhop S, Broderick AC, Conley DC, Cotterell SP, Crow E, Grecian WJ, Halsband C, Hodgson DJ, et al (2012). Assessing wave energy effects on biodiversity: the Wave Hub experience.
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences,
370(1959), 502-529.
Abstract:
Assessing wave energy effects on biodiversity: the Wave Hub experience
Marine renewable energy installations harnessing energy from wind, wave and tidal resources are likely to become a large part of the future energy mix worldwide. The potential to gather energy from waves has recently seen increasing interest, with pilot developments in several nations. Although technology to harness wave energy lags behind that of wind and tidal generation, it has the potential to contribute significantly to energy production. As wave energy technology matures and becomes more widespread, it is likely to result in further transformation of our coastal seas. Such changes are accompanied by uncertainty regarding their impacts on biodiversity. To date, impacts have not been assessed, as wave energy converters have yet to be fully developed. Therefore, there is a pressing need to build a framework of understanding regarding the potential impacts of these technologies, underpinned by methodologies that are transferable and scalable across sites to facilitate formal meta-analysis. We first review the potential positive and negative effects of wave energy generation, and then, with specific reference to our work at the Wave Hub (a wave energy test site in southwest England, UK), we set out the methodological approaches needed to assess possible effects of wave energy on biodiversity. We highlight the need for national and international research clusters to accelerate the implementation of wave energy, within a coherent understanding of potential effects-both positive and negative. © 2011 the Royal Society.
Abstract.
Witt MJ, Sheehan EV, Bearhop S, Broderick AC, Conley DC, Cotterell SP, Crow E, Grecian WJ, Halsband C, Hodgson DJ, et al (2012). Assessing wave energy effects on biodiversity: the Wave Hub experience. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 370(1959), 502-529.
Parnell AC, Phillips DL, Bearhop S, Semmens BX, Ward EJ, Moore JW, Jackson AL, Inger R (2012). Bayesian Stable Isotope Mixing Models.
Mainwaring MC, Hartley IR, Bearhop S, Brulez K, Du Feu CR, Murphy G, Plummer KE, Webber SL, James Reynolds S, Deeming DC, et al (2012). Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment. Journal of Biogeography
Mainwaring MC, Hartley IR, Bearhop S, Brulez K, du Feu CR, Murphy G, Plummer KE, Webber SL, James Reynolds S, Deeming DC, et al (2012). Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment.
Journal of Biogeography,
39(9), 1669-1677.
Abstract:
Latitudinal variation in blue tit and great tit nest characteristics indicates environmental adjustment
Aim the laying of eggs and the building of a nest structure to accommodate them are two of the defining characteristics of members of the class Aves. Nest structures vary considerably across avian taxa and for many species the structure of the completed nest can have important consequences both for parents and their offspring. While nest characteristics are expected to vary adaptively in response to environmental conditions, large-scale spatial variation in nest characteristics has been largely overlooked. Here, we examine the effects of latitudinal variation in spring temperatures on nest characteristics, including insulatory properties, and reproductive success of blue tits, Cyanistes caeruleus, and great tits, Parus major. Location Great Britain. Methods Nests and reproductive data were collected from seven study sites, spread over 5° of latitude. The nest insulatory properties were then determined before the nests were separated into nest base material and cup lining material. Results As spring temperatures increased with decreasing latitude, the mass of the nest base material did not vary in either species, while the mass of the cup lining material and nest insulatory properties decreased in both species. This suggests that in response to increasing temperatures the breeding female reduces the mass of the cup lining material, thereby maintaining an appropriate microclimate for incubating and brooding. The mean first egg date of both species advanced with decreasing latitude and increasing spring temperatures, although clutch size and brood size at hatching and fledging did not vary. Main conclusions This is the first study to demonstrate that the nest-construction behaviour of birds varies in response to large-scale spatial variation in ambient temperatures. Therefore, nest composition reliably indicates environmental conditions and we suggest that studies of nest structure may be sentinels for the early signs of rapid climate change. © 2012 Blackwell Publishing Ltd.
Abstract.
Fort J, Pettex E, Tremblay Y, Lorentsen SH, Garthe S, Votier S, Pons JB, Siorat F, Furness RW, Grecian WJ, et al (2012). Meta-population evidence of oriented chain migration in northern gannets (Morus bassanus).
Frontiers in Ecology and the Environment,
10(5), 237-242.
Abstract:
Meta-population evidence of oriented chain migration in northern gannets (Morus bassanus)
Although oriented migrations have been identified in many terrestrial bird species, the post-breeding-season movements of seabirds are generally regarded as dispersive. We used geolocator tags to reveal post-breeding movements and winter distribution of northern gannets (Morus bassanus) at a meta-population scale. By focusing on five breeding colonies of European gannets, we show that their breeding and wintering grounds are connected by a major flyway running along the coasts of Western Europe and Africa. Moreover, maximum winter distance to colony was similar across colonies despite their wide latitudinal range. In contrast with the general opinion that large pelagic birds such as gannets have unlimited ranges beyond the breeding season, our findings strongly suggest oriented chain migration in northern gannets (a pattern in which populations move uniformly southward) and highlight the benefit of meta-population approaches for studying seabird movements. We argue that the inclusion of such processes in ocean management plans is essential to improve efforts in marine biodiversity conservation. © the Ecological Society of America.
Abstract.
Drewe JA, Weber N, Carter SP, Bearhop S, Harrison XA, Dall SRX, McDonald RA, Delahay RJ (2012). Performance of proximity loggers in recording intra- and inter-species interactions: a laboratory and field-based validation study.
PLoS One,
7(6).
Abstract:
Performance of proximity loggers in recording intra- and inter-species interactions: a laboratory and field-based validation study
Knowledge of the way in which animals interact through social networks can help to address questions surrounding the ecological and evolutionary consequences of social organisation, and to understand and manage the spread of infectious diseases. Automated proximity loggers are increasingly being used to record interactions between animals, but the accuracy and reliability of the collected data remain largely un-assessed. Here we use laboratory and observational field data to assess the performance of these devices fitted to a herd of 32 beef cattle (Bos taurus) and nine groups of badgers (Meles meles, n = 77) living in the surrounding woods. The distances at which loggers detected each other were found to decrease over time, potentially related to diminishing battery power that may be a function of temperature. Loggers were highly accurate in recording the identification of contacted conspecifics, but less reliable at determining contact duration. There was a tendency for extended interactions to be recorded as a series of shorter contacts. We show how data can be manipulated to correct this discrepancy and accurately reflect observed interaction patterns by combining records between any two loggers that occur within a 1 to 2 minute amalgamation window, and then removing any remaining 1 second records. We make universally applicable recommendations for the effective use of proximity loggers, to improve the validity of data arising from future studies.
Abstract.
Lewison R, Oro D, Godley BJ, Underhill L, Bearhop S, Wilson RP, Ainley D, Arcos JM, Boersma PD, Borboroglu PG, et al (2012). Research priorities for seabirds: Improving conservation and management in the 21st century.
Endangered Species Research,
17(2), 93-121.
Abstract:
Research priorities for seabirds: Improving conservation and management in the 21st century
Seabirds are facing a growing number of threats in both terrestrial and marine habitats, and many populations have experienced dramatic changes over past decades. Years of seabird research have improved our understanding of seabird populations and provided a broader understanding of marine ecological processes. In an effort to encourage future research and guide seabird conservation science, seabird researchers from 9 nations identified the 20 highest priority research questions and organized these into 6 general categories: (1) population dynamics, (2) spatial ecology, (3) tropho-dynamics, (4) fisheries interactions, (5) response to global change, and (6) management of anthropogenic impacts (focusing on invasive species, contaminants and protected areas). For each category, we provide an assessment of the current approaches, challenges and future directions. While this is not an exhaustive list of all research needed to address the myriad conservation challenges seabirds face, the results of this effort represent an important synthesis of current expert opinion across sub-disciplines within seabird ecology. As this synthesis highlights, research, in conjunction with direct management, education, and community engagement, can play an important role in facilitating the conservation and management of seabird populations and of the ocean ecosystems on which they and we depend. © Inter-Research 2012.
Abstract.
Tosh DG, McDonald RA, Bearhop S, Llewellyn NR, Montgomery WI, Shore RF (2012). Rodenticide exposure in wood mouse and house mouse populations on farms and potential secondary risk to predators.
Ecotoxicology,
21(5), 1325-1332.
Abstract:
Rodenticide exposure in wood mouse and house mouse populations on farms and potential secondary risk to predators.
We compared capture rates and exposure to SGARs of wood mice (Apodemus sylvaticus) and house mice (Mus domesticus) in autumn/winter on farms that currently used, had previously used, and never used SGARs. 6-10 weeks after baiting programmes began, 15 % of 55 wood mice and 33 % of 12 house mice had detectable liver SGAR residues. Wood mice with residues occurred on farms not using rodenticides, reflecting the high mobility of these animals, and four had multiple liver residues, possibly due to cross-contamination of baits. The winter decline in wood mouse numbers was similar on farms that did and did not use SGARs, suggesting little long-term impact of SGARs on populations on farms. Our results indicate residual levels of rodenticides will be ever present in small mammal prey across the agricultural landscape unless all farms in a locality cease application. The implications for secondary exposure and poisoning of predators are discussed.
Abstract.
Author URL.
Stauss C, Bearhop S, Bodey TW, Garthe S, Gunn C, Grecian WJ, Inger R, Knight ME, Newton J, Patrick SC, et al (2012). Sex-specific foraging behaviour in northern gannets Morus bassanus: incidence and implications.
Marine Ecology Progress Series(457), 151-162.
Abstract:
Sex-specific foraging behaviour in northern gannets Morus bassanus: incidence and implications
Sexual segregation in foraging and migratory behaviour is widespread among sexually dimorphic marine vertebrates. It has also been described for a number of monomorphic species, yet the underlying mechanisms are poorly understood. We examined variation among years, seasons and age-classes in sex-specific foraging and over-wintering behaviour in the northern gannet (Morus bassanus), a species with slight sexual dimorphism. Our results revealed consistent sexual differences in the stable isotope ratios of breeding birds: over three different breeding periods, adult females consistently consumed prey with significantly lower δ13C and δ15N values than adult males. Additionally, GPS tracking data showed that breeding females foraged further offshore than breeding males (a result consistent with the δ13C data), and the home ranges of the two sexes were distinct. Analyses of stable isotope ratios using a Bayesian mixing model (SIAR) revealed that breeding males consumed a higher proportion of fishery discards than females. Analysis of stable isotope ratios in red blood cells of immature gannets (aged 2-4) indicated that sexual segregation was not present in this age class. Although sample sizes were small and statistical power correspondingly low, analysis of geolocator data and of stable isotope ratios in winter-grown flight feathers revealed no clear evidence of sexual segregation during the non-breeding period. Together these results provide a detailed insight into sex-specific behaviour in gannets throughout the annual cycle and although the mechanisms remain unclear they are unlikely to be explained by slight differences in size.
Abstract.
Robertson A, McDonald RA, Delahay RJ, Kelly SD, Bearhop S (2012). Whisker growth in wild Eurasian badgers Meles meles: implications for stable isotope and bait marking studies. European Journal of Wildlife Research, 1-10.
2011
Bodey TW, Mcdonald RA, Sheldon RD, Bearhop S (2011). Absence of effects of predator control on nesting success of Northern Lapwings Vanellus vanellus: Implications for conservation.
Ibis,
153(3), 543-555.
Abstract:
Absence of effects of predator control on nesting success of Northern Lapwings Vanellus vanellus: Implications for conservation
The control of generalist predator populations is increasingly adopted as a management tool to combat declines in ground-nesting bird populations. However, compensatory predation by uncontrolled species frequently occurs, so determining the relative impacts of different predatory species, and hence the relative benefits of their control, can be difficult. Islands, with their reduced faunas, provide natural experimental units for investigating specific predator-prey interactions in detail. We studied Northern Lapwing Vanellus vanellus breeding success on an island where feral Ferrets Mustela furo and Hooded Crows Corvus cornix were subjected to trial control regimes over 2years. In both years, Lapwing hatching success was >80%, with neither Ferret nor Crow control selected as important predictors. Fledging rates in both years were 0.7 young per pair, despite highly effective predator removal, although Crow control potentially resulted in compensatory predation by Common Ravens C. corax. Neither mustelid nor corvid control produced significant immediate benefits for Lapwings. This suggests that mesopredator release of mustelids in mainland situations is unlikely to be a consistent threat to Lapwing, and provides further evidence that declines in this species are unlikely to be tackled successfully through predator management alone. © 2011 the Authors. Ibis © 2011 British Ornithologists' Union.
Abstract.
Jackson AL, Inger R, Parnell A, Bearhop S (2011). Comparing isotopic niche widths among and within communities: SIBER - Stable Isotope Bayesian Ellipses in R.
Journal of Animal Ecology,
80(3), 595-602.
Abstract:
Comparing isotopic niche widths among and within communities: SIBER - Stable Isotope Bayesian Ellipses in R
1. The use of stable isotope data to infer characteristics of community structure and niche width of community members has become increasingly common. Although these developments have provided ecologists with new perspectives, their full impact has been hampered by an inability to compare statistically individual communities using descriptive metrics.
2. We solve these issues by reformulating the metrics in a Bayesian framework. This reformulation takes account of uncertainty in the sampled data and naturally incorporates error arising from the sampling process, propagating it through to the derived metrics.
3. Furthermore, we develop novel bivariate ellipse based metrics as an alternative to the currently employed Convex Hull methods when applied to single community members. We show that unlike Convex Hulls, the ellipses are unbiased with respect to sample size, and their estimation via Bayesian Inference allows robust comparison to be made among datasets comprising different sample sizes.
4. These new metrics open up more avenues for direct comparison of isotopic niches across communities. The computational code to calculate the new metrics is implemented in the free-to-download package SIAR for the R statistical environment.
Abstract.
Tosh DG, McDonald RA, Bearhop S, Lllewellyn NR, Fee S, Sharp EA, Barnett EA, Shore RF (2011). Does small mammal prey guild affect the exposure of predators to anticoagulant rodenticides?.
Environ Pollut,
159(10), 3106-3112.
Abstract:
Does small mammal prey guild affect the exposure of predators to anticoagulant rodenticides?
Ireland has a restricted small mammal prey guild but still includes species most likely to consume anticoagulant rodenticide (AR) baits. This may enhance secondary exposure of predators to ARs. We compared liver AR residues in foxes (Vulpes vulpes) in Northern Ireland (NI) with those in foxes from Great Britain which has a more diverse prey guild but similar agricultural use of ARs. Liver ARs were detected in 84% of NI foxes, more than in a comparable sample of foxes from Scotland and similar to that of suspected AR poisoned animals from England and Wales. High exposure in NI foxes is probably due to greater predation of commensal rodents and non-target species most likely to take AR baits, and may also partly reflect greater exposure to highly persistent brodifacoum and flocoumafen. High exposure is likely to enhance risk and Ireland may be a sentinel for potential effects on predator populations.
Abstract.
Author URL.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
MOLECULAR ECOLOGY,
20(22), 4786-4795.
Author URL.
Harrison XA, Bearhop S, Inger R, Colhoun K, Gudmundsson GA, Hodgson D, McElwaine G, Tregenza T (2011). Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Molecular ecology,
20(22), 4786-4795.
Abstract:
Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects.
Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced. © 2011 Blackwell Publishing Ltd.
Abstract.
Campos AR, Catry P, Tenreiro P, Neto JM, Pereira AC, Brito R, Cardoso H, Ramos JA, Bearhop S, Newton J, et al (2011). How do Robins Erithacus rubecula resident in Iberia respond to seasonal flooding by conspecific migrants?.
Bird Study,
58(4), 435-442.
Abstract:
How do Robins Erithacus rubecula resident in Iberia respond to seasonal flooding by conspecific migrants?
CapsuleThe majority of Robins in Iberia are sedentary and stay in their nesting areas despite the presumed increased competition that results from the seasonal flooding of the area by conspecific migrants. AimsTo evaluate if Robins in Iberia are displaced from their nesting areas by the presence of large numbers of competitors originating from higher latitudes. MethodsData from constant effort ringing sites were used to estimate the proportion of Robins that are strictly sedentary and the seasonal variation in Robin numbers. Hydrogen stable isotope ratios (2H) in feathers, and sex ratios determined through molecular techniques, allowed an insight into the numerical importance of invading Robins from higher latitudes. ResultsRobins were more numerous outside the breeding season, with clear influxes in autumn. Around half of the locally nesting Robins were captured during winter, indicating they are truly sedentary. 2H in feathers suggests that a wide mixture of Robins from all European latitudes were present in winter, and these data, together with sex ratios, suggest that there may be similar numbers of local and foreign individuals in winter at the main study site. ConclusionDespite the occupation of their range by migrants, local birds are largely sedentary. © 2011 British Trust for Ornithology.
Abstract.
Bodey TW, Bearhop S, McDonald RA (2011). Localised control of an introduced predator: creating problems for the future?.
Biol Invasions,
13(12), 2817-2828.
Abstract:
Localised control of an introduced predator: creating problems for the future?
Introduced mammalian predators have had significant impacts on many native prey species. Although control of such predators for conservation management is becoming increasingly commonplace, it is often undertaken at a relatively small scale in relation to the overall predator population. Processes such as immigration mean that it remains difficult to determine the effectiveness of control measures. We investigated the impacts of feral ferret Mustela furo removal on the entire feral ferret population on Rathlin Island, UK. Removal of ferrets prior to breeding led to a substantial increase in the post-dispersal population through the enhanced survival of juveniles. Despite increased numbers, overwinter survival remained high, potentially aided by the reduced territoriality shown by this feral species compared to wild carnivores. The response of this ferret population to control is a further illustration of the complex ecological processes and outcomes arising from the disruption of wildlife populations. It highlights how partial or localised management may prove ineffective, and at worst might exacerbate the problems that management was designed to avert.
Abstract.
Zbinden JA, Bearhop S, Bradshaw P, Gill B, Margaritoulis D, Newton J, Godley BJ (2011). Migratory dichotomy and associated phenotypic variation in marine turtles revealed by satellite tracking and stable isotope analysis.
Marine Ecology Progress Series,
421, 291-302.
Abstract:
Migratory dichotomy and associated phenotypic variation in marine turtles revealed by satellite tracking and stable isotope analysis
Linking foraging and breeding habitats is key to the understanding of behaviour, ecology and demography of migratory species Establishing such connections has long been hampered by the logistical problems of following individuals between foraging and breeding areas, especially in the marine realm We used variation in nitrogen stable isotope patterns between 2 foraging regions of loggerhead sea turtles Caretta caretta determined from samples of satellite-tracked individuals to assign untracked turtles to a foraging region We sought to enhance determination of the relative importance of geographically separated foraging regions and to investigate the relationship between fitness correlates and inferred migratory strategies of 18 turtles followed by satellite tracking from Zakynthos (Greece), 10 moved north to foraging areas in the Adriatic Sea and the Gulf of Amvrakikos and 8 moved south to foraging areas off the coast of North Africa of 51 untracked individuals sampled for stable isotope analysis, we considered the stable isotope signature of 47 to qualify for assignment to foraging areas in the north (n = 22) and south (n = 25) Females foraging north were significantly larger (curved carapace length), and the former group laid larger clutches (even after correction for body length) than turtles foraging south, a fact that can be interpreted as a carry-over effect Combining satellite tracking with stable isotope signatures in marine turtles opens new perspectives into how forensic tracking methodologies may be used to scale up knowledge from electronic tracking of a limited number of individuals to sample sizes that are more meaningful from a population perspective © Inter-Research 2011.
Abstract.
Phillips RA, McGill RAR, Dawson DA, Bearhop S (2011). Sexual segregation in distribution, diet and trophic level of seabirds: Insights from stable isotope analysis.
Marine Biology,
158(10), 2199-2208.
Abstract:
Sexual segregation in distribution, diet and trophic level of seabirds: Insights from stable isotope analysis
Considerable attention has focused on inter- and intraspecific variation in trophic niches of marine predators. Although this has revealed evidence for sexual segregation in distribution in some species, few studies have been able to address sex-related dietary specialisation. Stable isotope analysis of blood cells collected from albatrosses and petrels at South Georgia during chick-rearing indicated a difference in δ 13C, suggesting that females fed to the north of males, only in two species with male-biased sexual size dimorphism; in no species did sexes differ in trophic level (δ 15N). Based on a wider review, significant differences between sexes in isotope signatures were much more common in seabirds during the pre-laying or breeding than the nonbreeding period, presumably reflecting greater between-sex partitioning of resources when foraging ranges are more constrained and competition is greater. Sex differences, or their absence, were usually consistent across successive stages during the pre-laying and breeding periods, but not necessarily year-round nor between populations. Significant differences in isotope signatures between males and females were extremely rare in monomorphic species, suggesting a link between sexual size dimorphism and segregation in diet or distribution. Among the Southern Ocean albatrosses, sex differences in δ 13C suggested the underlying mechanism was related to habitat specialisation, whereas in other size-dimorphic taxa (both male- and female-biased), sex differences were more common in δ 15N than δ 13C and therefore more consistent with size-mediated competitive exclusion or dietary specialisation. © 2011 Springer-Verlag.
Abstract.
Bodey TW, Bearhop S, McDonald RA (2011). The diet of an invasive alien predator the feral ferret Mustela furo: implications for the conservation of ground nesting birds.
Eur J Wildl Res,
57, 107-117.
Abstract:
The diet of an invasive alien predator the feral ferret Mustela furo: implications for the conservation of ground nesting birds.
Introduced carnivores have had a significant impact on the fauna of a number of countries, particularly on islands. In the British Isles, several offshore islands holding internationally important aggregations of seabirds and shorebirds support self-sustaining feral ferret Mustela furo populations, often as the top terrestrial predator. However, little is known about the interactions between ferrets and both native and nonnative prey in these locations. We examined the diet of feral ferrets on Rathlin Island, Northern Ireland. We determined the frequency of occurrence of prey items and constructed energetic models to determine their potential impact on both native and introduced prey. Rabbits Oryctolagus cuniculus occurred in 75% of scats, while birds, carrion, and brown rats Rattus norvegicus were important secondary items. There was little difference between the diets of males and females. Estimates of the energy requirements of the population at current, and with hypothetically reduced, rabbit availability revealed the potential for carrion to maintain the ferret population over winter. Management options could thus focus on reducing anthropogenic food sources as an immediate way of mitigating the threat to ground-nesting birds, while other strategies, including eradication, are considered.
Abstract.
Tosh DG, Shore RF, Jess S, Withers A, Bearhop S, Ian Montgomery W, McDonald RA (2011). User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use.
J Environ Manage,
92(6), 1503-1508.
Abstract:
User behaviour, best practice and the risks of non-target exposure associated with anticoagulant rodenticide use.
Usage of anticoagulant rodenticides (ARs) is an integral component of modern agriculture and is essential for the control of commensal rodent populations. However, the extensive deployment of ARs has led to widespread exposure of a range of non-target predatory birds and mammals to some compounds, in particular the second-generation anticoagulant rodenticides (SGARs). As a result, there has been considerable effort placed into devising voluntary best practice guidelines that increase the efficacy of rodent control and reduce the risk of non-target exposure. Currently, there is limited published information on actual practice amongst users or implementation of best practice. We assessed the behaviour of a typical group of users using an on-farm questionnaire survey. Most baited for rodents every year using SGARs. Most respondents were apparently aware of the risks of non-target exposure and adhered to some of the best practice recommendations but total compliance was rare. Our questionnaire revealed that users of first generation anticoagulant rodenticides rarely protected or checked bait stations, and so took little effort to prevent primary exposure of non-targets. Users almost never searched for and removed poisoned carcasses and many baited for prolonged periods or permanently. These factors are all likely to enhance the likelihood of primary and secondary exposure of non-target species.
Abstract.
Author URL.
Robb GN, McDonald RA, Inger R, Reynolds SJ, Newton J, McGill RAR, Chamberlain DE, Harrison TJE, Bearhop S (2011). Using stable-isotope analysis as a technique for determining consumption of supplementary foods by individual birds.
Condor,
113(3), 475-482.
Abstract:
Using stable-isotope analysis as a technique for determining consumption of supplementary foods by individual birds
The amount of supplementary food humans provide to wild animals is increasing yet the full effects of this provisioning remain unclear. For these effects to be assessed at the levels of both the population and the individual, the degree to which individuals are using this resource must be quantified. Traditional approaches rely on observations of feeding animals and analysis of gut contents and feces, but these have several limitations. Stable-isotope analysis can overcome some of these. If supplementary food items are isotopically distinct from natural ones, the relative contribution of supplementary food to the diet may be quantified accurately. We demonstrate how the isotopic signature of supplementary foods can be manipulated to increase their discrimination from natural food sources and provide an example of the utility of this approach in a supplementary feeding study. We rovided supplementary food over a winter, then sampled birds during the following breeding season and analyzed their claws for their isotopic signature to estimate diet choices. The results highlight considerable variation in individuals' use of supplementary food, both within a study site and between different sites. Often the results from supplementation experiments are inconclusive. Even within the same species there can be an effect in one year or location but not in others, so a method for quantifying variation in food uptake could help in interpretation of the results. Stable-isotope analysis allows the effects of experimentally increased food supplies on ecology and behavior to be assessed accurately. © the Cooper Ornithological Society 2011.
Abstract.
Campos AR, Catry P, de Rojas M, Bearhop S, Ramos J, Newton J (2011). WINTER HABITAT INFLUENCES THE NUMBER OF FEATHER MITES OF TWO SPECIES LIVING ON EUROPEAN ROBINS ERITHACUS RUBECULA.
ARDEOLA-INTERNATIONAL JOURNAL OF ORNITHOLOGY,
58(1), 103-111.
Author URL.
Torres LG, Thompson DR, Bearhop S, Votier S, Taylor GA, Sagar PM, Robertson BC (2011). White-capped albatrosses alter fine-scale foraging behavior patterns when associated with fishing vessels.
Marine Ecology Progress Series,
428, 289-301.
Abstract:
White-capped albatrosses alter fine-scale foraging behavior patterns when associated with fishing vessels
Incidental bycatch of seabirds in commercial fishing activities is known to cause declines in seabird populations. However, the full impacts on the ecology of seabirds, including effects on seabird distribution and behavior, through the association with fisheries are not fully understood. We developed a novel method to integrate fine-scale GPS tracking data from the foraging trips of 25 white-capped albatross Thalassarche steadi within sub-Antarctic New Zealand with fishing effort distribution data to (1) quantify fine-scale overlap between individual albatrosses and individual vessels and (2) characterize behavioral changes in albatrosses when they are associated with fishing vessels. Overlap between vessels and albatrosses occurred in 68% of tracks. However, albatrosses demonstrated high variability in foraging trip destinations and association rates with fishing activity, both between and within individuals. Eight tracks never overlapped a fishing vessel. of the 17 tracks that did overlap, a range of 2 to 73% of foraging effort on each trip occurred while overlapping a fishing vessel. Albatross foraging behavior was characterized by a significantly slower and straighter path when overlapping vessels. This study highlights the utility of GPS tags to examine the fine-scale distribution of seabirds in relation to fishing activity, revealing how effects of fisheries on marine megafauna may extend beyond mortality and injury as well as population numbers. However, results are currently constrained, not only by limited tracking data sets, but also by the quality (spatio- temporal resolution) and availability of fishing effort data. Critical conservation issues related to the effects of fisheries on threatened marine megafauna cannot be fully addressed without comparative data sets with resolution equal to GPS tags. ©Inter-Research 2011.
Abstract.
2010
Bodey TW, Bearhop S, Roy SS, Newton J, McDonald RA (2010). Behavioural responses of invasive American mink Neovison vison to an eradication campaign, revealed by stable isotope analysis.
Journal of Applied Ecology,
47(1), 114-120.
Abstract:
Behavioural responses of invasive American mink Neovison vison to an eradication campaign, revealed by stable isotope analysis
1. The detrimental impacts of invasive, non-native species on islands are widely acknowledged and it is often best to act rapidly against such species, even where uncertainty exists over the best way to proceed. If management actions are evaluated and refined, using information learnt from the biology of culled animals, this uncertainty can be gradually reduced, increasing the likelihood of a successful outcome.
2. American mink Neovison vison carcasses were collected as part of an eradication campaign on several islands of the Outer Hebrides, Scotland, and stable isotope analysis was used to describe ecological variation in this invasive non-native predator.
3. Isotope profiles from individual mink whiskers demonstrated how behaviour at a population level changed markedly over time. As the eradication campaign progressed, mink increased their reliance on marine food sources and focused their activity on the coastline. Stable isotope analyses also demonstrated sex-related changes in foraging and ranging behaviour in relation to food resource availability on the two main island complexes.
4. Synthesis and applications. Our findings contribute to the refinement of a campaign to extend the successful eradication of mink from Uist and Harris, to the whole of the Outer Hebrides archipelago, UK. They also highlight the potential for stable isotope approaches to provide more detailed postmortem information that can inform adaptive management of wildlife populations for conservation objectives.
Abstract.
Inger R, Harrison XA, Ruxton GD, Newton J, Colhoun K, Gudmundsson GA, McElwaine G, Pickford M, Hodgson D, Bearhop S, et al (2010). Carry-Over Effects Reveal Reproductive Costs in a Long Distance Migrant. Journal of Animal Ecology, 79, 974-982.
Harrison XA, Blount J, Inger R, Bearhop S (2010). Carry-over Effects as Drivers of Fitness in Animals. Journal of Animal Ecology, 79, 974-982.
Harrison XA, Tregenza T, Inger R, Colhoun K, Dawson DA, Gudmundsson GA, Hodgson DJ, Horsburgh GJ, McElwaine G, Bearhop S, et al (2010). Cultural inheritance drives site fidelity and migratory connectivity in a long-distance migrant.
MOLECULAR ECOLOGY,
19(24), 5484-5496.
Author URL.
Inger R, McDonald RA, Rogowski D, Jackson AL, Parnell A, Preston SJ, Harrod C, Goodwin C, Griffiths D, Dick JTA, et al (2010). Do non-native invasive fish support elevated lamprey populations?.
Journal of Applied Ecology,
47, 121-129.
Abstract:
Do non-native invasive fish support elevated lamprey populations?
Summary
1. Managing populations of predators and their prey to achieve conservation or resource management goals is usually technically challenging and frequently socially controversial. This is true even in the simplest ecosystems but can be made much worse when predator-prey relationships are influenced by complex interactions, such as biological invasions, population trends or animal movements.
2. Lough Neagh in Northern Ireland is a European stronghold for pollan Coregonus autumnalis, a coregonine fish, and for river lamprey Lampetra fluviatilis, which feeds parasitically as an adult. Both species are of high conservation importance. Lampreys are known to consume pollan but detailed knowledge of their interactions is scant. While pollan is well known to be a landlocked species in Ireland, the life cycle of normally anadromous river lamprey in Lough Neagh has been unclear. The Lough is also a highly perturbed ecosystem, supporting several invasive, non-native fish species that have the potential to influence lamprey-pollan interactions.
3. We applied stable isotope techniques to resolve both the movement patterns of lamprey and trophic interactions in this complex community. Recognising that stable isotope studies are often hampered by high-levels of variability and uncertainty in the systems of interest, we employed novel Bayesian mixing models, which incorporate variability and uncertainty.
4. Stable isotope analyses identified trout Salmo trutta and non-native bream Abramis brama as the main items in lamprey diet. Pollan only represented a major food source for lamprey between May and July.
5. Stable isotope ratios of carbon in tissues from 71 adult lamprey showed no evidence of marine carbon sources, strongly suggesting that Lough Neagh is host to a highly unusual, non-anadromous freshwater population. This finding marks out the Lough’s lamprey population as of particular scientific interest and enhances the conservation significance of this feature of the Lough.
6. Synthesis and applications. Our Bayesian isotopic mixing models illustrate an unusual pattern of animal movement, enhancing conservation interest in an already threatened population. We have also revealed a complex relationship between lamprey and their food species that is suggestive of hyperpredation, whereby non-native species may sustain high lamprey populations that may in turn be detrimental to native pollan. Long-term conservation of lamprey and pollan in this system is likely to require management intervention, but in light of this exceptional complexity, no simple management options are currently supported. Conservation plans will require better characterisation of population-level interactions and simulation modelling of interventions. More generally our study demonstrates the importance of considering a full range of possible trophic interactions, particularly in complex ecosystems, and highlights Bayesian isotopic mixing models as powerful tools in resolving trophic relationships.
Abstract.
Author URL.
Harrison TJE, Smith JA, Martin GR, Chamberlain DE, Bearhop S, Robb GN, Reynolds SJ (2010). Does food supplementation really enhance productivity of breeding birds?.
Oecologia,
164(2), 311-320.
Abstract:
Does food supplementation really enhance productivity of breeding birds?
Food availability influences multiple stages of the breeding cycle of birds, and supplementary feeding has helped in its understanding. Most supplementation studies have reported advancements of laying, whilst others, albeit less numerous, have also demonstrated fitness benefits such as larger clutches, shorter incubation periods, and greater hatching success. Relatively few studies, however, have investigated the effects of supplementary feeding for protracted periods across multiple stages of the breeding cycle. These effects are important to understand since long-term food supplementation of birds is recommended in urban habitats and is used as a tool to increase reproductive output in endangered species. Here, we compare the breeding phenology and productivity of blue tits Cyanistes caeruleus and great tits Parus major breeding in food-supplemented and non-supplemented blocks in a broadleaf woodland in central England over three seasons (2006-2008). Supplementation was provided continuously from several weeks pre-laying until hatching, and had multiple significant effects. Most notably, supplementation reduced brood size significantly in both species, by half a chick or more at hatching (after controlling for year and hatching date). Reduced brood sizes in supplemented pairs were driven by significantly smaller clutches in both species and, in blue tits, significantly lower hatching success. These are novel and concerning findings of food supplementation. As expected, supplementary feeding advanced laying and shortened incubation periods significantly in both species. We discuss the striking parallels between our findings and patterns in blue and great tit reproduction in urban habitats, and conclude that supplementary feeding may not always enhance the breeding productivity of birds.
Abstract.
Author URL.
Anderson ORJ, Phillips RA, Shore RF, McGill RAR, McDonald RA, Bearhop S (2010). Element patterns in albatrosses and petrels: influence of trophic position, foraging range, and prey type.
Environ Pollut,
158(1), 98-107.
Abstract:
Element patterns in albatrosses and petrels: influence of trophic position, foraging range, and prey type.
We investigated the concentrations of 22 essential and non-essential elements among a community of Procellariiformes (and their prey) to identify the extent to which trophic position and foraging range governed element accumulation. Stable isotope analysis (SIA) was used to characterise trophic (delta(15)N) and spatial patterns (delta(13)C) among species. Few consistent patterns were observed in element distributions among species and diet appeared to be highly influential in some instances. Arsenic levels in seabird red blood cells correlated with delta(15)N and delta(13)C, demonstrating the importance of trophic position and foraging range for arsenic distribution. Arsenic concentrations in prey varied significantly across taxa, and in the strength of association with delta(15)N values (trophic level). In most instances, element patterns in Procellariiformes showed the clearest separation among species, indicating that a combination of prey selection and other complex species-specific characteristics (e.g. moult patterns) were generally more important determining factors than trophic level per se.
Abstract.
Author URL.
Votier SC, Bearhop S, Witt MJ, Inger R, Thompson D, Newton J (2010). Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems.
Journal of Applied Ecology,
47(2), 487-497.
Abstract:
Individual responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems
The large amount of discards produced by commercial fisheries can have major impacts on marine predator populations: this abundant food may increase populations of some scavengers or decrease others via accidental bycatch. Yet, despite the conservation implications of discard practices, the ecology of individual scavengers is poorly understood. Here, we assess the influence of commercial fisheries' activity on the foraging behaviour of individual breeding northern gannets Morus bassanus. Using recent developments in stable isotope mixing models (Stable Isotope Analysis in R or SIAR) we estimate individual discard consumption. Using GPS tracking and the Vessel Monitoring System (VMS), we investigate behavioural responses to trawlers. Analysis of conventional diet samples, as well as stable isotope ratios of carbon and nitrogen in blood (plasma and cells), highlight marked individual differences in the proportion of fishery discards in the diet. Individual differences in foraging behaviour revealed by stable isotopes show evidence of both short-term consistency and behavioural flexibility. At-sea path tortuosity of 25 gannets (tracked using GPS loggers) revealed scale-dependent adjustments in response to VMS-derived fishing vessel locations, as well as to sea surface temperature, chlorophyll a concentration and copepod abundance. The results also indicate individual variability in behavioural response to trawlers. Individual differences in the amount of discards estimated from SIAR were negatively correlated with differences in foraging trip length and body condition, indicating potential fitness consequences. Synthesis and applications. The management of commercial fisheries and apex predators is a daunting task. Ultimately, reducing bycatch and removing dependency on discards remain key conservation priorities, but managers should also ensure that scavenging species have sufficient alternative food to meet their energetic needs, to ameliorate potential unforeseen knock-on consequences. The results of Stable Isotope Analysis (SIAR) reveal intra-population differences in discard consumption by gannets; differences that have impacts on foraging effort and body condition. The use of GPS tracking and Vessel Monitoring Systems (VMS) reveal that gannet at-sea behaviour is influenced by fishing vessels, although this also varies among individuals. A combination of SIAR, GPS tracking and VMS can be used to study fishery/scavenger interactions in detail at the individual level, to answer fundamental questions about scavenging behaviour. © 2010 the Authors. Journal compilation © 2010 British Ecological Society.
Abstract.
Votier S, Bearhop S, Witt M, Inger R, Thompson D, Newton J (2010). Individual-level responses of seabirds to commercial fisheries revealed using GPS tracking, stable isotopes and vessel monitoring systems. Journal of Applied Ecology, 47, 487-497.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 2, 365-371.
Harrison XA, Dawson DA, Horsburgh GJ, Tregenza T, Bearhop S (2010). Isolation, characterisation and predicted genome locations of Light-bellied Brent goose (Branta bernicla hrota) microsatellite loci (Anatidae, AVES). Conservation Genetics Resources, 1-7.
Grecian WJ, Inger R, Attrill MJ, Bearhop S, Godley BJ, Witt MJ, Votier SC (2010). Potential impacts of wave-powered marine renewable energy installations on marine birds.
Ibis,
152, 683-697.
Abstract:
Potential impacts of wave-powered marine renewable energy installations on marine birds
One potential approach to combat the impacts of climate change is the expansion of renewable energy installations, leading to an increase in the number of wave-powered marine renewable energy installations (MREIs). The consequences of increased use of these devices for birds are unknown. Here we describe the wave-powered energy- generating devices currently either operational or in development and review the potential threats and benefits of these to marine birds, their habitats and prey. Direct neg- ative effects include risk of collision, disturbance, displacement and redirection during construction, operation and decommissioning. Above-water collision is a particular con- cern with wind-powered devices, but, because of their low profiles, the collision risk asso- ciated with wave-powered devices is likely to be much lower. Conversely, wave devices also pose the novel threat of underwater collision. Wave-energy-generating devices may indirectly impact marine birds by altering oceanographic processes and food availability, with implications for trophic cascades. Through appropriate mitigation, wave-powered MREIs offer the potential to enhance habitats. Direct positive effects may include provision of roosting sites, and indirect positive effects may include prey aggregation due to suitable substrates for sessile organisms or because they act as de facto protected areas. The cumulative effect of these could be the improvement and protection of foraging opportunities for marine birds. Recent studies have been critical of the methods used in the assessment of wind-powered MREI impacts, which lack sufficient sample sizes, controls or pre-development comparisons. Here we suggest solutions for the design of future studies into the effects of MREIs. Wave-powered MREIs are certain to become part of the marine environment, but with appropriate planning, mitigation and monitor- ing they have the potential to offer benefits to marine birds in the future.
Abstract.
Mangel JC, Alfaro-Shigueto J, Van Waerebeek K, Cáceres C, Bearhop S, Witt MJ, Godley BJ (2010). Small cetacean captures in Peruvian artisanal fisheries: High despite protective legislation.
Biological Conservation,
143(1), 136-143.
Abstract:
Small cetacean captures in Peruvian artisanal fisheries: High despite protective legislation
We detail the first direct, at sea monitoring of small cetacean interactions with Peruvian artisanal drift gillnet and longline fisheries. A total of 253 small cetaceans were captured during 66 monitored fishing trips (Gillnet: 46 trips; Longline: 20 trips) from the port of Salaverry, northern Peru (8o14′S, 78o59′W) from March 2005 to July 2007. The most commonly captured species were common dolphins (Delphinus spp.) (47%), dusky dolphins (Lagenorhynchus obscurus) (29%), common bottlenose dolphins (Tursiops truncatus) (13%) and Burmeister's porpoises (Phocoena spinipinnis) (6%). An estimated 95% of common dolphin bycatch was of long-beaked common dolphins (Delphinus capensis). Overall bycatch per unit effort for gillnet vessels (mean ± sd) was estimated to be 0.65 ± 0.41 animals.set-1 (range 0.05-1.50) and overall catch (bycatch and harpoon) was 4.96 ± 3.33 animals.trip-1 (range 0.33-13.33). Based upon total fishing effort for Salaverry we estimated the total annual average small cetacean bycatch by gillnet vessels as 2412 animals.year-1 (95% CI 1092-4303) for 2002-2007. This work indicates that, in at least one Peruvian port, bycatch and harpooning of small cetaceans persist at high levels and on a regular basis, particularly in driftnet vessels, despite the existence since the mid-1990s of national legislation banning the capture of marine mammals and commerce in their products. It is concluded that the coast of Peru is likely still one of the world's principal areas for concern regarding high small cetacean bycatch and there is clearly an urgent need to increase the geographic scope of observer effort to elucidate the full magnitude of this issue. © 2009 Elsevier Ltd. All rights reserved.
Abstract.
Parnell A, Inger R, Bearhop S, Jackson AL (2010). Source partitioning using stable isotopes: coping with variation.
Plos One,
3(5).
Abstract:
Source partitioning using stable isotopes: coping with variation.
Stable isotope analysis is increasingly being utilised across broad areas of ecology and biology. Key to much of this work is the use of mixing models to estimate the proportion of sources contributing to a mixture such as in diet estimation. By accurately reflecting natural variation and uncertainty to generate robust probability estimates of source proportions, the application of Bayesian methods to stable isotope mixing models promises to enable researchers to address an array of new questions, and approach current questions with greater insight and honesty. We outline a framework that builds on recently published Bayesian isotopic mixing models and present a new open source R package, SIAR. The formulation in R will allow for continued and rapid development of this core model into an all-encompassing single analysis suite for stable isotope research.
Abstract.
Rutz CR, Bluff LA, Reed N, Troscianko J, Newton J, Inger R, Kacelnik A, Bearhop S (2010). The Ecological Significance of Tool Use in New Caledonian Crows.
Science,
329, 1523-1525.
Abstract:
The Ecological Significance of Tool Use in New Caledonian Crows
Tool use is so rare in the animal kingdom that its evolutionary origins cannot be traced with comparative analyses. Valuable insights can be gained from investigating the ecological context and adaptive significance of tool use under contemporary conditions, but obtaining robust observational data is challenging. We assayed individual-level tool-use dependence in wild
New Caledonian crows by analyzing stable isotope profiles of the birds’ feathers, blood, and putative food sources. Bayesian diet-mixing models revealed that a substantial amount of the crows’ protein and lipid intake comes from prey obtained with stick tools—wood-boring beetle larvae. Our calculations provide estimates of larva-intake rates and show that just a few larvae can satisfy a crow’s daily energy requirements, highlighting the substantial rewards available to competent tool users.
Abstract.
2009
Anderson ORJ, Phillips RA, Shore RF, McGill RAR, McDonald RA, Bearhop S (2009). Diet, individual specialisation and breeding of brown skuas (Catharacta antarctica lonnbergi): an investigation using stable isotopes.
Polar Biology,
32(1), 27-33.
Abstract:
Diet, individual specialisation and breeding of brown skuas (Catharacta antarctica lonnbergi): an investigation using stable isotopes
The diet of brown skuas (Catharacta antarctica lonnbergi) on Bird Island, South Georgia was assessed using a combination of stable isotope analysis (SIA) and mixing model techniques. We found evidence that individual specialisation in diet of adult brown skuas was related to timing of breeding, which may reflect differences in intrinsic quality. Adults with more enriched 13C values hatched chicks earlier than those with depleted 13C values. Individuals with enriched 13C fed predominantly on Antarctic fur seal (Arctocephalus gazella) carrion and placenta while those with lower ratios appeared to rely more on burrowing petrels (e.g. Antarctic prions Pachyptila desolata). Individual foraging differences clearly influenced timing of breeding and potentially the reproductive output of breeding pairs. We confirmed that the main components of the diet of brown skuas during incubation are, in decreasing order of importance, Antarctic fur seal placenta, burrowing petrels and fur seal muscle. In addition, we identified fur seal faeces in the diet during this stage, which had not been detected previously by traditional sampling methods. Finally we identified a correlation in δ13C values between pair members, attributable to the influence of courtship feeding of females by males, or assortative mating according to foraging preference or intrinsic quality. © 2008 Springer-Verlag.
Abstract.
Jackson AL, Inger R, Bearhop S, Parnell A (2009). Erroneous behaviour of MixSIR, a recently published Bayesian isotope mixing model: a discussion of Moore & Semmens (2008).
Ecol Lett,
12(3), E1-E5.
Abstract:
Erroneous behaviour of MixSIR, a recently published Bayesian isotope mixing model: a discussion of Moore & Semmens (2008).
The application of Bayesian methods to stable isotopic mixing problems, including inference of diet has the potential to revolutionise ecological research. Using simulated data we show that a recently published model MixSIR fails to correctly identify the true underlying dietary proportions more than 50% of the time and fails with increasing frequency as additional unquantified error is added. While the source of the fundamental failure remains elusive, mitigating solutions are suggested for dealing with additional unquantified variation. Moreover, MixSIR uses a formulation for a prior distribution that results in an opaque and unintuitive covariance structure.
Abstract.
Author URL.
Mainwaring MC, Rowe LV, Kelly DJ, Grey J, Bearhop S, Hartley IR (2009). Hatching asynchrony and growth trade-offs within Barn Swallow broods.
Condor,
111(4), 668-674.
Abstract:
Hatching asynchrony and growth trade-offs within Barn Swallow broods
Hatching asynchrony results in age and size hierarchies within broods, and the subsequent asymmetric competition among siblings has important consequences for nestlings' fitness. In this study, we compare the growth of Barn Swallow (Hirundo rustica) nestlings in relation to their order of hatching. The aim was to test the prediction that early-hatched nestlings develop differently from late-hatched nestlings, which should be under greater pressure to trade investment in growth in favor of traits important to simultaneous fledging. Early-hatched nestlings were always larger than late-hatched nestlings, but when the age difference was taken into account, the two classes of nestling gained mass and head-bill length in similar ways, including having similar asymptotes, as predicted by nonlinear curve models. For wing length, however, late-hatched nestlings reached the inflection point of growth sooner than early-hatched nestlings, and although scaled rates of wing growth were similar, earlyhatched nestlings had significantly longer wings, both before fledging, when the oldest nestling was 14 days old, and as suggested by the asymptotic, age-independent values derived from the nonlinear curve models. This finding suggests that nestlings hatched later preferentially develop body mass and the skeleton at the expense of wing feathers. As swallows rely on their wings for foraging and avoiding predators, this pattern of resource allocation is likely to have negative consequences for the late-hatched nestlings. © the Cooper Ornithological Society 2009.
Abstract.
Anderson ORJ, Phillips RA, McDonald RA, Shore RF, McGill RAR, Bearhop S (2009). Influence of trophic position and foraging range on mercury levels within a seabird community.
Marine Ecology Progress Series,
375, 277-288.
Abstract:
Influence of trophic position and foraging range on mercury levels within a seabird community
Seabirds are often advocated as biomonitors for marine contaminants such as mercury (Hg). However, contaminant levels can vary widely depending on among-individual and among-species variation in foraging preferences and physiology, and on tissue types used for analyses. Using stable isotope analysis (SIA), we investigated the effects of trophic position, season, and tissue type on Hg burdens in a group of 10 closely related seabirds (Procellariiformes) from a single colony in the South Atlantic. Analysis of blood (reflecting breeding season diet) showed that among-species Hg concentrations varied as a function of trophic position (δ15N) and were also influenced to a lesser degree by foraging range (δ13C). This pattern did not hold for feathers, which reflect the non-breeding period. Mercury levels in feathers formed during the non-breeding season appear to be more strongly governed by species effects (such as moult schedule), demonstrating the need to carefully consider tissue type when formulating predictions regarding Hg burdens and dynamics. Assessment at a community rather than the species level, and across a number of tissue types, provided a more complete picture of the complex interactions between Hg and foraging ecology in seabirds. © Inter-Research 2009.
Abstract.
Inger R, Attrill MJ, Bearhop S, Broderick AC, Grecian WJ, Hodgson DJ, Sheehan E, Votier SC, Witt MJ, Godley BJ, et al (2009). Marine Renewable Energy: potential benefits to biodiversity? an urgent call for research.
Journal of Applied Ecology,
46, 1145-1153.
Abstract:
Marine Renewable Energy: potential benefits to biodiversity? an urgent call for research.
1. The evidence for anthropogenically induced climate change is overwhelming with the production of greenhouse gases from burning fossil fuels being a key driver. In response, many governments have initiated programmes of energy production from renewable sources.
2. The marine environment presents a relatively untapped energy source and offshore installations are likely to produce a significant proportion of future energy production. Wind power is the most advanced, with development of wave and tidal energy conversion devices expected to increase worldwide in the near future.
3. Concerns over the potential impacts on biodiversity of marine renewable energy installations (MREI) include: habitat loss, collision risks, noise and electromagnetic fields. These factors have been posited as having potentially important negative environmental impacts.
4. Conversely, we suggest that if appropriately managed and designed, MREI may increase local biodiversity and potentially benefit the wider marine environment. Installations have the capacity to act as both artificial reefs and fish aggregation devices, which have been used previously to facilitate restoration of damaged ecosystems, and de facto marine-protected areas, which have proven successful in enhancing both biodiversity and fisheries.
5. The deployment of MREI has the potential to cause conflict among interest groups including energy companies, the fishing sector and environmental groups. Conflicts should be minimized by integrating key stakeholders into the design, siting, construction and operational phases of the installations, and by providing clear evidence of their potential environmental benefits.
6. Synthesis and applications. MREI have the potential to be both detrimental and beneficial to the environment but the evidence base remains limited. To allow for full biodiversity impacts to be assessed, there exists an urgent need for additional multi and inter-disciplinary research in this area ranging from engineering to policy. Whilst there are a number of factors to be considered, one of the key decisions facing current policy makers is where installations should be sited, and, dependent upon site, whether they should be designed to either minimize negative environmental impacts or as facilitators of ecosystem restoration.
Abstract.
Author URL.
Inger R, Attrill MJ, Bearhop S, Broderick AC, James Grecian W, Hodgson DJ, Mills C, Sheehan E, Votier SC, Witt MJ, et al (2009). Marine renewable energy: Potential benefits to biodiversity? an urgent call for research.
Journal of Applied Ecology,
46(6), 1145-1153.
Abstract:
Marine renewable energy: Potential benefits to biodiversity? an urgent call for research
The evidence for anthropogenically induced climate change is overwhelming with the production of greenhouse gases from burning fossil fuels being a key driver. In response, many governments have initiated programmes of energy production from renewable sources. 2. The marine environment presents a relatively untapped energy source and offshore installations are likely to produce a significant proportion of future energy production. Wind power is the most advanced, with development of wave and tidal energy conversion devices expected to increase worldwide in the near future. 3. Concerns over the potential impacts on biodiversity of marine renewable energy installations (MREI) include: habitat loss, collision risks, noise and electromagnetic fields. These factors have been posited as having potentially important negative environmental impacts. 4. Conversely, we suggest that if appropriately managed and designed, MREI may increase local biodiversity and potentially benefit the wider marine environment. Installations have the capacity to act as both artificial reefs and fish aggregation devices, which have been used previously to facilitate restoration of damaged ecosystems, and de facto marine-protected areas, which have proven successful in enhancing both biodiversity and fisheries. 5. The deployment of MREI has the potential to cause conflict among interest groups including energy companies, the fishing sector and environmental groups. Conflicts should be minimized by integrating key stakeholders into the design, siting, construction and operational phases of the installations, and by providing clear evidence of their potential environmental benefits. 6. Synthesis and applications. MREI have the potential to be both detrimental and beneficial to the environment but the evidence base remains limited. To allow for full biodiversity impacts to be assessed, there exists an urgent need for additional multi and inter-disciplinary research in this area ranging from engineering to policy. Whilst there are a number of factors to be considered, one of the key decisions facing current policy makers is where installations should be sited, and, dependent upon site, whether they should be designed to either minimize negative environmental impacts or as facilitators of ecosystem restoration. © 2009 British Ecological Society.
Abstract.
Bodey TW, McDonald RA, Bearhop S (2009). Mesopredators constrain a top predator: competitive release of ravens after culling crows.
Biol Lett,
5(5), 617-620.
Abstract:
Mesopredators constrain a top predator: competitive release of ravens after culling crows.
Although predator control programmes rarely consider complex competitive interactions among predators, it is becoming clear that removal of larger 'superior' competitors often releases the 'inferior' ones and can precipitate trophic cascades. In contrast, our study indicates that culling hooded crows Corvus cornix appears to release a larger competitor, the common raven Corvus corax. Ravens ranged more widely, and the predation of artificial nests was significantly faster (although total predation was similar), after the removal of crows. Our study provides evidence of a novel reversal of competitive release where a larger species was freed from constraints imposed on its distribution and behaviour by a smaller species, and emphasizes the importance of considering community and ecosystem effects of predator manipulations when undertaken for conservation or game management.
Abstract.
Author URL.
Phillips RA, Bearhop S, McGill RAR, Dawson DA (2009). Stable isotopes reveal individual variation in migration strategies and habitat preferences in a suite of seabirds during the nonbreeding period.
Oecologia,
160(4), 795-806.
Abstract:
Stable isotopes reveal individual variation in migration strategies and habitat preferences in a suite of seabirds during the nonbreeding period.
Information on predator and prey distributions is integral to our understanding of migratory connectivity, food web dynamics and ecosystem structure. In marine systems, although large animals that return to land can be fitted with tracking devices, minimum instrument sizes preclude deployments on small seabirds that may nevertheless be highly abundant and hence major consumers. An increasingly popular approach is to use N and C stable isotope analysis of feathers sampled at colonies to provide information on distribution and trophic level for the preceding, and generally little-known, nonbreeding period. Despite the burgeoning of this research, there have been few attempts to verify such relationships. In this study, we demonstrate a clear correspondence between isotope ratios of feathers and nonbreeding distributions of seven species from South Georgia tracked using loggers. This generated a rudimentary isoscape that was used to infer the habitat preferences of eight other species ranging in size from storm petrels to albatrosses, and which could be applied, with caveats, in other studies. Differences in inferred distribution within and between species had major implications for relative exposure to anthropogenic threats, including climate change and fisheries. Although there were no differences in isotope values between sexes in any of the smaller petrels, mean stable C (delta(13)C), but not stable N isotope ratios (delta(15)N), tended to be greater in females than males of the larger, and more sexually size-dimorphic species. This indicates a difference in C source (distribution), rather than trophic level, and a correspondence between the degree of sexual size dimorphism in Procellariiformes and the level of between-sex niche segregation.
Abstract.
Author URL.
2008
Inger R, Bearhop S (2008). Applications of stable isotope analyses to avian ecology.
Ibis,
150(3), 447-461.
Abstract:
Applications of stable isotope analyses to avian ecology
In the past 20 years the use of stable isotope analysis has become increasingly common in ecological studies. In fact, in some instances these techniques have yielded remarkable insights into the foraging preferences and migrations of birds. Despite these advances and the potential of the approach, it is possibly still not as widely used as might be expected. In this paper we aim to illustrate the potential of the approach in the hope of encouraging more avian ecologists to think again about how these techniques might provide insights in the systems on which they work. We discuss some of the principles behind the approach, and review some of the more recent ornithological studies that have used stable isotope techniques to trace trophic pathways or infer migratory origins. We follow this by discussing some of the latest ideas on how stable isotopes may be used to generate community metrics and close by detailing the important assumptions and caveats that should be considered before undertaking any studies using this technique. © 2008 the Authors.
Abstract.
Crawford K, McDonald RA, Bearhop S (2008). Applications of stable isotope techniques to the ecology of mammals.
Mammal Review,
38(1), 87-107.
Abstract:
Applications of stable isotope techniques to the ecology of mammals
1. Stable isotope analysis (SIA) has the potential to become a widespread tool in mammalian ecology, because of its power in resolving the ecological and behavioural characteristics of animals. Although applications of the technique have enhanced our understanding of mammalian biology, it remains underused. Here we provide a review of previous applications to the study of extant mammals, drawing when appropriate on examples from the wider ecological literature, to identify the potential for future development of the approach. 2. Stable isotope analysis has been applied successfully to understanding the basic foraging decisions of mammals. However, SIA generates quantitative data on a continuous scale meaning that the approach can be particularly powerful in the characterization of community metrics, such as dimensions of resource partitioning within species assemblages or nutrient dynamics in food chains. Resolving spatial and temporal patterns of individual, intraspecific and interspecific resource use is of fundamental importance in animal ecology and evolutionary biology and SIA will emerge as a critical tool in these fields. 3. Geographical differences in naturally occurring stable isotopes have allowed ecologists to describe large-scale mammal migrations. Several isotopic gradients exist at smaller spatial scales, which can provide finer resolution of spatial ecology. 4. A combination of foraging and movement decisions is of prime importance in the study of ecotoxicology, since this discipline requires quantitative understanding of exposure risk. © Journal compilation © 2008 Mammal Society.
Abstract.
Robb GN, McDonald RA, Chamberlain DE & Bearhop S (2008). Food for thought: supplementary feeding as a driver of ecological change in avian populations. Frontiers in Ecology, 6
Kelly JF, Bearhop S, Bowen GJ, Hobson KA, Norris DR, Wassenaar LI, West JB, Wunder MB (2008). Future Directions and Challenges for Using Stable Isotopes in Advancing Terrestrial Animal Migration Research.
Terrestrial Ecology,
2, 129-139.
Abstract:
Future Directions and Challenges for Using Stable Isotopes in Advancing Terrestrial Animal Migration Research
The intent of this volume was to provide the reader with a comprehensive background needed to understand the potential and the state-of-the-art in the application of stable isotope tools to the study of animal migration, and to encourage new research endeavors. Animal migration remains an exciting field that will provide many years of research for scientists in numerous disciplines. We have hopefully conveyed the idea that stable isotopes are not a "silver bullet" that will provide unambiguous insight into animal origins. The true potential of the isotope techniques will only be realized in cases where the researcher has been careful to first choose the species and migratory system that shows promise isotopically, and then considers the sources of variance in the model used to infer origins. The path ahead will involve far more emphasis on understanding the mechanisms that can influence isotopic variation spatially and within organisms of interest. It will also involve more careful consideration of how we statistically infer origins or establish the probability of assignment. Use of more refined isoscape models that involve several elements and the careful use of new remote sensing GIS layers will also be a fruitful area of research. Obviously, these areas of research and development are likely well beyond the scope of any single researcher or laboratory, and hence this field is sure to emerge as one of the best examples of multidisciplinary collaborative research. © 2008 Elsevier Inc. All rights reserved.
Abstract.
Inger R, Gudmundsson GA, Ruxton GD, Newton J, Colhoun K, Auhage S, Bearhop S (2008). Habitat utilisation during staging affects body condition in a long distance migrant, Branta bernicla hrota: Potential impacts on fitness?.
Journal of Avian Biology,
39(6), 704-708.
Abstract:
Habitat utilisation during staging affects body condition in a long distance migrant, Branta bernicla hrota: Potential impacts on fitness?
There is considerable evidence to suggest that an animal's ability to access the appropriate resources at one time of year may profoundly restrict its performance at another. For migrants, wintering and breeding periods are often connected by refuelling or staging periods, critical (particularly for females) in attaining the body reserves required to ensure successful breeding. However in many instances there are differences in the extent to which different individuals gain access to the highest quality resources. Here we demonstrate how body condition in brent geese Branta bernicla hrota, during spring staging is related to differences in marine and terrestrial habitat utilisation (inferred from stable isotope analysis). Female birds with high fat scores feed to a greater extent on marine resources. Body mass and condition are also higher in individuals utilising more marine resources. Given that body mass at spring staging is correlated with reproductive success, the extent of marine habitat maybe critical to this population. Combining this with data from previous studies of dark-bellied brent geese Branta bernicla bernicla, we predict the potential impacts of spring staging resource utilisation on future breeding success. Although staging is of short duration compared to the other components of annual cycles of migratory species, our results suggest that the quality of staging grounds may be vitally important to population processes. © 2008 the Authors.
Abstract.
Oswald SA, Bearhop S, Furness RW, Huntley B, Hamer KC (2008). Heat stress in a high-latitude seabird: Effects of temperature and food supply on bathing and nest attendance of great skuas Catharacta skua.
Journal of Avian Biology,
39(2), 163-169.
Abstract:
Heat stress in a high-latitude seabird: Effects of temperature and food supply on bathing and nest attendance of great skuas Catharacta skua
Birds such as great skuas Catharacta skua adapted for successful breeding at high latitudes may experience problems of heat dissipation in mild climates. Great skuas spend time bathing at freshwater sites close to breeding territories and here, we examine impacts of heat stress on bathing, foraging and nest attendance of adults during three breeding seasons with marked variation in the availability of prey (1-group sandeels Ammodytes marinus). Adults exhibited diurnal variation in bathing activity that matched heat-stress conditions. Moreover more birds bathed on days of higher average heat stress, suggesting that bathing plays a role in thermoregulation. Bathing numbers were lower in years of poor food availability, when adult attendance at territories was low, probably because lower attendance reduced the opportunity for parents to bathe without leaving chicks unattended. Chicks are normally guarded by female parents and fed by males but under conditions of low food availability territorial attendance of breeding pairs was particularly low on days of high heat stress, with chicks regularly left unattended at air temperatures exceeding 14°C. Unattended chicks are at risk of being killed by neighbouring conspecifics and survival of chicks to fledging was low in the two years of low sandeel stocks. Our study indicates that for great skuas, indirect effects of climate change on prey stocks and direct effects on heat stress experienced by adults may be additive. © Journal of Avian Biology.
Abstract.
Votier SC, Bearhop S, Attrill MJ & Oro D (2008). Is climate change the most likely driver of range expansion for a critically endangered top predator in northeast Atlantic waters?. Biology Letters, 4, 205-206.
Votier SC, Bearhop S, Fyfe R, Furness RW (2008). Temporal and spatial variation in the diet of a marine top predator-links with commercial fisheries.
Marine Ecology Progress Series,
367, 223-232.
Abstract:
Temporal and spatial variation in the diet of a marine top predator-links with commercial fisheries
The huge quantities of waste produced by commercial fisheries worldwide attract large numbers of scavengers. Reducing this wasteful practice is desirable, but may have implications for marine ecosystems as scavengers will face a major shortfall in food. Predicting the impact of reduced discarding requires information on the strength of the link between scavengers and fisheries. We analysed sagittal otoliths regurgitated by great skuas Stercorarius skua over 5 yr from 8 different colonies in Shetland, UK, and over 18 yr from 1 of these sites, in relation to spatial and temporal variation in fisheries activity. The proportions of 2 demersal fish not normally available to skuas, haddock Melanogrammus aeglefinus and whiting Merlangius merlangus, are positively correlated with annual variation in discard estimates. The proportion of whiting at 8 colonies is positively correlated with spatial differences in fish biomass estimates, and blue whiting Micromesistus potassou are only eaten in colonies close to the continental shelf edge, where this species is fished. Non-breeding great skuas tend to eat smaller and significantly more variable discarded fish compared with breeders. Our results indicate that great skuas rely heavily on fishery discards and are also sensitive to spatial and temporal changes in fisheries activity. Differences between breeding status indicate that the nonbreeding component of the population may respond differently to changing discard policy. The strength of the link between fisheries and scavengers appear to be species-specific, and testing the strength of these relationships should be an important avenue of future research to interpret the response of scavengers to changes in fisheries management. © Inter-Research 2008.
Abstract.
Fox T, Bearhop S (2008). The use of stable-isotope ratios in ornithology.
British Birds,
101(3), 112-130.
Abstract:
The use of stable-isotope ratios in ornithology
The use of mass spectrometry to analyse the stable-isotope ratios of bird tissues has become an important new tool for research ornithologists in the last 20 years. Because stable isotopes vary geographically and according to specific biological processes in the environment, they provide a unique forensic means of understanding more about avian biology and ecology than we can learn using conventional techniques alone. The stable-isotope ratios present in different tissues of birds reflect the ratios in the environment at the time those tissues were constructed. However, because of the rapid turnover of some tissues compared with others, an individual bird will bear within its body constituents a record of its present and past exposure to different isotopic environments. Because the stable-isotope ratios of specific elements vary geographically (e.g. hydrogen along oceanic to continental gradients) and between habitats (e.g. nitrogen and carbon in marine versus terrestrial ecosystems), they offer a unique means of studying the ways migratory birds move between different parts of the planet and of understanding the habitats they exploit. This review looks at some of the innovative ways in which the technique has been used in a variety of recent studies of birds. The technique is not restricted to breaking new ground in high science; in terms of understanding migration strategies, the importance of breeding, migratory and wintering habitat and the feeding ecology of birds, the study of stable-isotope ratios is becoming ever more important in supporting conservation actions. © British Birds.
Abstract.
Robb GN, McDonald RA, Chamberlain DE, Reynolds SJ, Harrison TJE & Bearhop S (2008). Winter feeding of birds increases productivity in the subsequent breeding season. Biology Letters, 4, 220-223.
2007
Newsome SD, Rio CMD, Bearhop S, Phillips DL (2007). A niche for isotopic ecology. Frontiers in Ecology and the Environment, preprint(2007).
Newsome SD, Martinez del Rio C, Bearhop S, Phillips DL (2007). A niche for isotopic ecology. Frontiers in Ecology and the Environment, 5(8), 429-429.
delRio, C.M. Bearhop, S. Phillips, D.L. (2007). A niche for isotopic ecology. Frontiers in Ecology and the Environment, 5, 429-436.
Catry, P. Silk, J.R.D. Bearhop, S. (2007). Movements, winter distribution and activity patterns of Falkland and brown skuas: insights from loggers and isotopes. Marine Ecology Progress Series, 345, 281-291.
Bearhop, S. (2007). Seabird predation by great skuas Stercorarius skua - intra-specific competition for food?. Journal of Avian Biology, 38, 234-246.
Bearhop, S. Lecoq, M. (2007). Sex differences in settlement behaviour and condition of chiffchaffs Phylloscopus collybita at a wintering site in Portugal. Are females doing better?. Journal of Ornithology, 148, 241-249.
Kennedy, M. Bearhop, S. (2007). Supplementary DNA evidence fails to confirm presence of Brown Skuas Stercorarius antarctica in Europe: a retraction of Votier et al. Ibis, 149, 619-621.
Furness RW, Crane JE, Bearhop S, Garthe S, Kakela A, Kakela R, Kelly A, Kubetzki U, Votier SC & Waldron S (2007). Techniques to link individual migration patterns of seabirds with diet specialization, condition and breeding performance. Ardea, 94, 631-638.
Christensen, T.K. Bearhop, S. Newton, J. (2007). Using stable isotope analysis of multiple feather tracts to identify moulting provenance of vagrant birds: a case study of Baikal Teal Anas formosa in Denmark. Ibis, 149, 622-625.
2006
Bearhop S (2006). Change in the air. Natural History, 115
Votier SC, Crane JE, Bearhop S, de Leon A, McSorley CA, Minguez E, Mitchell IP, Parsons M, Phillips RA & Furness RW (2006). Nocturnal foraging by great skuas Stercorarius skua: implications for conservation of storm-petrel populations. Journal of Ornithology, 147, 405-413.
Bearhop, S. Robinson, J.A. Ruxton, G.D. (2006). Prey Choice Affects the Trade Off Balance in an Avian Herbivore. Animal Behaviour, 71: 1335-1341
Phillips, R.A. McGill, R. Cherel, Y. (2006). Stable isotopes indicate sex-specific and long-term individual foraging specialisation in diving seabirds. Marine Ecology Progress Series, 311, 157-164.
Ruxton, G.D. Newton, J. Colhoun, K. (2006). Temporal and intrapopulation variation in prey choice of wintering geese determined by stable isotope analysis. Journal of Animal Ecology, 75: 1190-1200
SBearhop, Colhoun K, Inger R, Mackie K (2006). Using daily ration models and stable isotope analysis to predict biomass depletion by herbivores. Journal of Applied Ecology, 43(5), 1022-1030.
2005
SBearhop, Fielder W, Furness RW, Votier SC (2005). Assortative Mating as a Mechanism for Rapid Evolution of a Migratory Divide. Science, 310(5747), 502-504.
Bearhop S, Fiedler W, Furness RW, Votier SC, Waldron S, Newton J, Bowen GJ, Berthold P, Farnsworth K (2005). Evolution: Assortative mating as a mechanism for rapid evolution of a migratory divide.
Science,
310(5747), 502-504.
Abstract:
Evolution: Assortative mating as a mechanism for rapid evolution of a migratory divide
There have been numerous recent observations of changes in the behavior and dynamics of migratory bird populations, but the plasticity of the migratory trait and our inability to track small animals over large distances have hindered investigation of the mechanisms behind migratory change. We used habitat-specific stable isotope signatures to show that recently evolved allopatric wintering populations of European blackcaps Sylvia atricapilla pair assortatively on their sympatric breeding grounds. Birds wintering further north also produce larger clutches and fledge more young. These findings describe an important process in the evolution of migratory divides, new migration routes, and wintering quarters. Temporal segregation of breeding is a way in which subpopulations of vertebrates may become isolated in sympatry.
Abstract.
Bearhop, S. Thompson, D.R. (2005). Shape can influence the rate of colony fragmentation in ground nesting seabirds. Oikos, 111: 473 -478
Thompson DR, Bearhop S, Ross B (2005). Spread of Australasian pipit (Anthus novaeseelandiae) onto Campbell Island following eradication of Norway rats (Rattus norvegicus). Notornis, 52(1), 43-46.
2004
Clark RG, Hobson KA, Nichols JD, Bearhop S (2004). Avian Dispersal and Demography: Scaling up to the Landscape and Beyond. The Condor, 106(4), 717-719.
Clark RG, Hobson KA, Nichols JD & Bearhop S (2004). Avian dispersal ad demogrgaphy: Scaling up to the landscape and beyond. Condor, 106, 717-719.
SBearhop, Crane JE, Furness RW, Votier SC (2004). Changes in fisheries discard rates and seabird communities. Nature, 427(6976), 727-730.
SBearhop, Adams CE, Fuller RA, Waldron S (2004). Determining trophic niche width: a novel approach using stable isotope analysis. Journal of Animal Ecology, 73(5), 1007-1012.
Votier SC, Bearhop S, Newell RG, Orr K, Furness RW, Kennedy M (2004). Erratum: the first record of Brown Skua Catharacta antarctica in Europe (IBIS (2004) 146 (95-102)). Ibis, 146(2).
Bearhop, S. Ratcliffe, N. Phillips, R.A. (2004). Predation by great skuas at a large Shetland seabird colony. Journal of Applied Ecology, 41: 1117-1128
Votier SC, Bearhop S, Ratcliffe N, Furness RW (2004). Reproductive Consequences for Great Skuas Specializing as Seabird Predators. The Condor, 106(2), 275-287.
Bearhop, S. Ratcliffe, N. Furness, R.W. (2004). Reproductive consequences for great skuas specializing as seabird predators. Condor, 106: 275-287
Hilton, G. Votier, S.C. Waldron, S. (2004). Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat. Proceedings of the Royal Society B, 271(Supp 4), S215-S218.
Votier SC, Bearhop S, Newell RG, Orr K, Furness RW, Kennedy M (2004). The first record of Brown Skua Catharacta antarctica in Europe.
Ibis,
146(1), 95-102.
Abstract:
The first record of Brown Skua Catharacta antarctica in Europe
Evidence from mtDNA suggests that two skuas, one discovered in the Scilly Islands Corn-wall in October 2001, the other in Glamorgan in February 2002, belong to the Brown Skua group Catharacta antarctica - a species not previously recorded in the North Atlantic. These molecular data do not exclude the possibility of either bird being a hybrid between Brown Skua and South Polar Skua C. maccormicki, but population estimates suggest that this is unlikely. More importantly, biometrics show that the Glamorgan bird is much smaller than hybrids but matches Falkland Skua C. a. antarctica. The distributions of C. antarctica sub-species at sea are not well known, but the discovery of two of these birds in the UK suggests that they may wander more extensively than previously thought.
Abstract.
Votier SC, Bearhop S, Newell RG, Orr K, Furness RW & Kennedy M (2004). The first record of Brown Skua Catharacta antarctica in Eurpoe. Ibis, 146
2003
Furness, R.W. Hilton, G. Votier, S.C. (2003). A forensic approach to understanding diet and habitat use from stable isotope analysis of (avian) claw material. Functional Ecology, 17: 270-275
Votier SC, Bearhop S, MacCormick A, Ratcliffe N & Furness RW (2003). Assessing the diet of great skuas, Catharacta skua, using five different techniques. Polar Biology, 26, 20-26.
Bearhop S, Ward RM & Evans PR (2003). Long-term survival rates in colour-ringed shorebirds - practical considerations in the application of mark-recapture models. Bird Study, 50, 271-279.
2002
Waldron, S. Votier, S.C. Furness, R.W. (2002). Factors influencing turnover and fractionation of nitrogen and carbon stable isotopes in avian blood and feathers. Physiological and Biochemical Zoology, 75: 451-458
Bearhop S, Waldron S, Votier SC & Furness RW (2002). Factors that influence assimilation rates and fractionation of nitrogen and carbon stable isotopes in avian blood and feathers. Physiological and Biochemical Zoology, 75, 451-458.
Arcos JM, Ruiz X, Bearhop S & Furness RW (2002). Mercury levels in seabirds and their fish prey at the Ebro Delta (NW Mediterranean): the role of trawler discards as a source of contamination. Marine Ecology Progress Series, 232, 281-290.
2001
Bearhop S, Thompson DR, Phillips RA, Waldron S, Hamer KC, Gray CM, Votier SC, Ross BP, Furness RW (2001). Annual Variation in Great Skua Diets: the Importance of Commercial Fisheries and Predation on Seabirds Revealed by Combining Dietary Analyses. The Condor, 103(4), 802-809.
Thompson, D.R. Phillips, R.A. Waldron, S. (2001). Annual variation in great skua diets: the importance of commercial fisheries and predation on seabirds revealed by combining dietary analyses. Condor, 103: 802-809
Donnelly T, Waldron S, Tait A, Dougans J & Bearhop S (2001). Hydrogen isotope analysis of natural abundance and deuterium-enriched waters by reduction over chromium on-line to a dynamic dual inlet isotope-ratio mass spectrometer. Rapid Communications in Mass Spectrometry, 15, 1297-1303.
Votier SC, Bearhop S, Ratcliffe N & Furness RW (2001). Pellets as indicators of diet in Great Skuas Catharacta skua. Bird Study, 48, 373-376.
2000
Bearhop S, Waldron S, Thompson D, Furness R (2000). Bioamplification of mercury in great skua Catharacta skua chicks: the influence of trophic status as determined by stable isotope signatures of blood and feathers.
Marine Pollution Bulletin,
40(2), 181-185.
Abstract:
Bioamplification of mercury in great skua Catharacta skua chicks: the influence of trophic status as determined by stable isotope signatures of blood and feathers
Biomagnification of mercury was investigated via combined mercury and stable isotope analysis of the blood and feathers of great skua chicks from two colonies in the north-east Atlantic. There were significant positive correlations between δ15N signatures and mercury concentrations in the blood from chicks at both colonies suggesting that dietary specialization influences intra-specific variability in mercury burdens. The relationships were slightly weaker in feathers and therefore blood is probably a better monitoring unit. Adult blood was also assessed and in terms of biomonitoring may provide an index of mercury intake over the whole breeding season. (C) 2000 Elsevier Science Ltd.
Abstract.
Bearhop S, Ruxton GD, Furness RW (2000). Dynamics of mercury in blood and feathers of great skuas.
Environmental Toxicology and Chemistry,
19(6), 1638-1643.
Abstract:
Dynamics of mercury in blood and feathers of great skuas
Mercury dynamics in the blood and feathers of captive great skuas, Catharacta skua, were monitored over 56 weeks. Prior to the onset of molt, mercury intake was solely from their maintenance ration of sprats, Sprattus sprattus. For the first half of molt, in addition to mercury intake from sprats, birds were fed different doses of methylmercuric chloride weekly for 20 weeks. During the second half of molt, dosing was stopped and mercury intake was solely from sprats. Blood was sampled throughout the study and feather growth was monitored. Prior to the onset of molt, mercury concentrations increased over the first 51 to 71 d and appeared to level off after this period. Repeated dosing models based on mammalian pharmacokinetics were, in general, too simplistic to be applicable to the birds in the study. During molt, the elimination of mercury from the blood is probably best described by a three-compartment model. Mercury concentrations in feathers were significantly correlated with those in blood at the time of their growth, suggesting that blood and feathers reflect mercury intake over the same time period. Individuals varied in their ability to excrete ingested mercury into the feathers.
Abstract.
Bearhop S, Waldron S, Furness RW (2000). Influence of Lipid and Uric Acid on δ. 13. C and δ. 15. N Values of Avian Blood: Implications for Trophic Studies. Ornithology, 117(2), 504-507.
Bearhop S, Teece MA, Waldron S, Furness RW (2000). Influence of lipid and uric acid on δ<sup>13</sup>C and δ<sup>15</sup>N values of avian blood: Implications for trophic studies. Auk, 117(2), 504-507.
Bearhop S, Phillips RA, Thompson DR, Waldron S, Furness RW (2000). Variability in mercury concentrations of great skuas Catharacta skua: the influence of colony, diet and trophic status inferred from stable isotope signatures.
Marine Ecology Progress Series,
195, 261-268.
Abstract:
Variability in mercury concentrations of great skuas Catharacta skua: the influence of colony, diet and trophic status inferred from stable isotope signatures
A range of parameters thought to contribute to intra-specific variation in mercury levels were investigated using the feathers and blood of adult great skuas Catharacta skua from 2 northeast Atlantic colonies as sampling units. Different feather types and blood were taken to represent intake over different temporal scales. Mercury concentrations and stable isotope signatures of these tissues were determined. General linear models demonstrated that trophic status, as indicated by δ15N, had an influence on tissue mercury concentrations. However this effect was relatively minor compared to that of foraging area. Samples of the same feather types from the same individuals in consecutive years suggest that a factor other than dietary specialisation and foraging area is of major importance in determining intra-specific variability in mercury levels. It was concluded that there are a number of interacting factors contributing to intra-specific variability in mercury levels and the relative importance of these factors varies both spatially and temporally.
Abstract.
1999
Bearhop S, Griffiths R, Orr K, Furness RW (1999). Mean corpuscular volume (MCV) as a measure of condition in birds.
Ecology Letters,
2(6), 352-356.
Abstract:
Mean corpuscular volume (MCV) as a measure of condition in birds
Haematological parameters, particularly haematocrit, are frequently used in assessing condition in birds. Mean corpuscular volume (MCV) overcomes some of the drawbacks associated with measuring haematocrits and therefore should be a better condition index. We investigated the relationship between these blood parameters and the breeding performances of great skuas Catharacta skua. As predicted from activity budgets of the sexes, male MCVs were significantly positively correlated with hatch date and the MCVs of both sexes were negatively correlated with the number of chicks fledged. No correlations existed between these breeding parameters and haematocrit. Since males provision females and chicks, they probably influence breeding performance via foraging abilities, whereas in females nutritional investment may be more important. This is the first study of a free-living/nondomesticated vertebrate population in which these kinds of relationship have been demonstrated and we conclude that MCV is a useful measure of condition.
Abstract.
Phillips RA, Bearhop S, Hamer KC, Thompson DR (1999). Rapid population growth of great skuas catharacta skua at st kilda: Implications for management and conservation.
Bird Study,
46(2), 174-183.
Abstract:
Rapid population growth of great skuas catharacta skua at st kilda: Implications for management and conservation
The St Kilda archipelago is a World Heritage Site holding internationally important populations of a number of seabird species. Great Skuas first bred at St Kilda in 1963, and numbers there rose steadily until 1990. Since then, a rapid expansion has occurred, with the population size increasing on Hirta, the main island in the archipelago, at a rate of 22.1% per annum between 1994 and 1997. In total, 233 pairs were occupying territories at St Kilda in 1997. A simple model suggests that as many as 50% of the birds recruited to Hirta between 1994 and 1997 were immigrants from other colonies. Comparison of breeding data collected in different areas gave no indication that the higher nest density resulting from the recent influx was having any detrimental effect on annual productivity and it seems likely that Great Skuas will continue to increase, at least in the near future. Given the importance of seabird prey in the diet of Great Skuas at St Kilda, the continued expansion in numbers of this species gives some cause for concern. However, because immigration plays a large role in the population dynamics of Great Skuas at this site, any attempts to limit population growth by small-scale culling of adults or reduction of reproductive output is unlikely to succeed, and might result in a decline in recruitment at other colonies of this rare and vulnerable species. © 1999 Taylor & Francis Group, LLC.
Abstract.
Bearhop S, Thompson DR, Waldron S, Russell IC, Alexander G, Furness RW (1999). Stable isotopes indicate the extent of freshwater feeding by cormorants Phalacrocorax carbo shot at inland fisheries in England.
Journal of Applied Ecology,
36(1), 75-84.
Abstract:
Stable isotopes indicate the extent of freshwater feeding by cormorants Phalacrocorax carbo shot at inland fisheries in England
1. The numbers of cormorants Phalacrocorax carbo feeding at English freshwater fisheries during winter have increased rapidly over the last 20 years, causing concern among fishery managers and anglers. 2. In order to assess the extent of freshwater feeding, stable isotope ratios of carbon and nitrogen (δ13C and δ15N) in feathers of wild cormorants from inland freshwater fisheries were compared with those in the feathers of piscivorous birds with marine diets (captive 'marine-fed' cormorants, free-ranging shags Phalacrocorax aristotelis) and freshwater diets (juvenile goosanders Mergus merganser). 3. Isotope signatures of feathers represent the diet at the time of growth. Feathers grown at different times of the year were taken from wild cormorants; each feather type therefore represented the diet over a different temporal scale. 4. Isotopic analyses of feathers indicated that, when shot, nearly all of the cormorants had been feeding entirely on freshwater prey. The mean δ13C value of primary feathers growing when birds were shot was -22-2‰, indicative of an entirely freshwater diet. 5. The move to freshwater habitats from coastal breeding grounds occurred over several months, but once established cormorants appear to have fed at freshwater sites throughout the autumn and winter. 6. The suitability of using a two-source isotopic mixing model in order to quantify the extent of freshwater feeding in piscivorous birds is discussed. 7. Although the results indicate long-term residency and feeding in freshwater systems, they do not indicate whether birds were feeding regularly at the sites at which they were shot, or the composition of the diet. It is recommended that further studies using telemetry and multiple isotope analyses be carried out in order to address these issues.
Abstract.
Monteiro LR, Ramos JA, Pereira JC, Monteiro PR, Feio RS, Thompson DR, Bearhop S, Furness RW, Laranjo M, Hilton G, et al (1999). Status and distribution of Fea's Petrel, Bulwer's Petrel, Manx Shearwater, Little Shearwater and Band-rumped Storm-petrel in the Azores archipelago.
Waterbirds,
22(3), 358-366.
Abstract:
Status and distribution of Fea's Petrel, Bulwer's Petrel, Manx Shearwater, Little Shearwater and Band-rumped Storm-petrel in the Azores archipelago
This paper reports the first comprehensive surveys of Fea's Petrel (Pterodroma feae), Bulwer's Petrel (Bulweria bulwerii), Manx Shearwater (Puffinus puffinus), Little Shearwater (Puffinus assimilis baroli) and two temporally-segregated forms of Band-rumped Storm-petrel (Oceanodroma castro) in the whole Azores archipelago, conducted from 1996 to 1998. Listening to nocturnal vocalizations was the main survey method. Breeding of Fea's Petrel was not confirmed and new sites of Bulwer's Petrel were not found (previous status: one site, 50 pairs), but previously undocumented colonies were identified for the remaining species. Manx Shearwater occurred in four colonies with 115-235 pairs (previous status: probable breeder), Little Shearwater occurred in 28 colonies with 840-1,530 pairs (previously: four locations, >150 pairs), hot-season Band-rumped Storm-petrels occurred in 5 colonies with 250-300 pairs (previously: two locations, 200 pairs) and cool-season Band-rumped Storm-petrels were found in eight locations with 665-740 pairs (previously: three locations, 600 pairs). Most colonies were confined to precipitous cliffs and islets, which may be a result of predation threats by introduced mammals. Although these surveys provided a valuable revision of the status and distribution for these species of conservation concern, further survey work is warranted and target areas are indicated. We discuss the potential and limitations of listening for nocturnal vocalizations as a method to survey and monitor shearwater and petrel populations in inaccessible habitats. Received 24 May 1999, accepted 8 July 1999.
Abstract.
Bearhop S, Griffiths R, Orr K, Furness RW (1999). The normal haematology of great skuas (Catharacta skua) in the wild.
Comparative Clinical Pathology,
9(2), 107-109.
Abstract:
The normal haematology of great skuas (Catharacta skua) in the wild
Routine haematological investigations were carried out on 102 wild adult great skuas Catharacta skua. No sex- or age-related differences were detected in any of the parameters measured. There are very few sets of haematological reference ranges published for seabirds from the northeastern Atlantic. Given the recent pollution threats in this region, the reference ranges presented for this species could be a valuable tool in future conservation efforts. © 1999 Springer-Verlag London Limited.
Abstract.
Bearhop S, Griffiths R, Orr K, Furness RW (1999). The normal haematology of great skuas (Catharacta skua) in the wild.
Comparative Haematology International,
9(2), 107-109.
Abstract:
The normal haematology of great skuas (Catharacta skua) in the wild
Routine haematological investigations were carried out on 102 wild adult great skuas Catharacta skua. No sex- or age-related differences were detected in any of the parameters measured. There are very few sets of haematological reference ranges published for seabirds from the northeastern Atlantic. Given the recent pollution threats in this region, the reference ranges presented for this species could be a valuable tool in future conservation efforts.
Abstract.
1998
Thompson DR, Bearhop S, Speakman JR, Furness RW (1998). Feathers as a means of monitoring mercury in seabirds: Insights from stable isotope analysis.
Environ Pollut,
101(2), 193-200.
Abstract:
Feathers as a means of monitoring mercury in seabirds: Insights from stable isotope analysis.
Mercury concentrations, together with nitrogen and carbon stable isotope signatures, were determined in body feather samples from northern fulmars Fulmarus glacialis and great skuas Catharacta skua, and in different flight feathers from great skuas. There were no significant relationships between trophic status, as defined using isotope analysis, and mercury concentration in the same feather type, in either species. Mercury concentrations in body feather samples were markedly different between fulmars and skuas, reflecting differences in diet, but there was no corresponding difference in trophic status as measured through nitrogen stable isotope signatures. We conclude that mercury concentrations and stable isotope values in feathers are uncoupled, mercury concentrations apparently reflecting the body pool of accumulated mercury at the time of feather growth whilst stable isotope values reflect the diet at the time of feather growth. There were significant positive correlations between the different flight feathers of great skuas for all three parameters measured. These were strongest between primary 10 and secondary 8, suggesting that these two feathers are replaced at the same time in the moult sequence in great skuas. Stable isotope analysis of different feathers may provide a means of investigating moult patterns in birds.
Abstract.
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