The Experts below are selected from a list of 204 Experts worldwide ranked by ideXlab platform
Keith C Hamer - One of the best experts on this subject based on the ideXlab platform.
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effects of windscape on three dimensional foraging behaviour in a wide ranging marine predator the Northern Gannet
Marine Ecology Progress Series, 2019Co-Authors: Jude V Lane, D V Spracklen, Keith C HamerAbstract:Marine birds are strongly exposed to weather conditions at sea but to date, few studies have investigated the influences of wind or rainfall on their time-activity budgets or foraging routines. Here, we used data from GPS and pressure loggers to investigate the effects of wind speed and direction and rainfall on the 3-dimensional foraging behaviour of Gannets Morus bassanus breeding at Bass Rock, Scotland. We found that birds spent more time actively foraging during stronger winds, but there was no subsequent increase in overall trip duration because individuals compensated by decreasing the time they spent on the water during stronger winds. Birds returned more quickly from distant foraging grounds, and those encountering head winds spent less time on the water and so were able to compensate to some extent for an adverse effect of head winds on speed of travel over the return leg. These data strongly suggest that by reducing time spent on the water, birds were able to buffer trip durations against adverse effects of strong winds encountered during both commuting and active foraging. Birds also commuted at greater heights with increasing tail wind speed and at lower heights with increasing head wind speed, potentially providing an additional behavioural buffer against the adverse effects of strong head winds during foraging trips. There was no discernible effect of rain on foraging, but the behavioural flexibility recorded here is likely to be critical to maintaining nest attendance patterns and food provisioning rates of chicks across variable environmental conditions encountered at sea.
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sex differences in migration and demography of a wide ranging seabird the Northern Gannet
Marine Ecology Progress Series, 2019Co-Authors: Zoe Deakin, Stuart Bearhop, Thomas W Bodey, Bethany L Clark, James Grecian, Keith C Hamer, Richard B Sherley, Matt Gummery, Jude V Lane, Greg MorganAbstract: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) 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.
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frequency and consequences of individual dietary specialisation in a wide ranging marine predator the Northern Gannet
Marine Ecology Progress Series, 2018Co-Authors: Stephen C Votier, Thomas W Bodey, Keith C Hamer, Samantha C Patrick, Ian R Cleasby, Jason Newton, Ewan D Wakefield, Stuart BearhopAbstract:Individual specialisations in animals are important contributors to a wide range of ecological and evolutionary processes, and have been particularly documented in relation to multiple aspects of foraging behaviours. Central-place foragers, such as seabirds, frequently exhibit pronounced specialisations and individual differences in a variety of foraging traits. In particular, the availability of fisheries discards alongside natural prey resources provides additional potential for differentiation and specialisation for opportunistically scavenging seabird species. However, the consequences of such specialisations for at-sea distributions and intraspecific interactions are not well known. Here, we investigated the links between the degree of dietary specialisation on natural or discarded prey and the foraging movements and spatial occupancy of Northern Gannets Morus bassanus in relation to differing intraspecific competition at 6 colonies of differing sizes. We found that, at most colonies, individuals with different dietary strategies concentrated foraging at differing levels of intraspecific competition. In addition, individuals pursuing different strategies were frequently, but not consistently, spatially separated, distinctions that were most acutely seen in females. However, this variation in individual strategy had no significant impact on current body condition. These analyses demonstrate how foraging-associated metrics need not covary within an unconstrained system. They also reveal that specialisation can have important consequences for the competitive regimes individuals experience, highlighting the complexity of examining interacting consequences at large spatial scales.
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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, 2017Co-Authors: Stephen C Votier, Annette L Fayet, Stuart Bearhop, Thomas W Bodey, Bethany L Clark, James Grecian, Tim Guilford, Keith C Hamer, Jana W E Jeglinski, Greg MorganAbstract:Individual foraging specializations, where individuals use a small component of the population niche width, are widespread in nature with important ecological and evolutionary implications. In long-lived animals, foraging ability develops with age, but we know little about the ontogeny of individuality in foraging. Here we use precision global positioning system (GPS) loggers to examine how individual foraging site fidelity (IFSF), a common component of foraging specialization, varies between breeders, failed breeders and immatures in a long-lived marine predator-the Northern Gannet Morus bassanus Breeders (aged 5+) showed strong IFSF: they had similar routes and were faithful to distal points during successive trips. However, centrally placed immatures (aged 2-3) were far more exploratory and lacked route or foraging site fidelity. Failed breeders were intermediate: some with strong fidelity, others being more exploratory. Individual foraging specializations were previously thought to arise as a function of heritable phenotypic differences or via social transmission. Our results instead suggest a third alternative-in long-lived species foraging sites are learned during exploratory behaviours early in life, which become canalized with age and experience, and refined where possible-the exploration-refinement foraging hypothesis. We speculate similar patterns may be present in other long-lived species and moreover that long periods of immaturity may be a consequence of such memory-based individual foraging strategies.
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seabird movement reveals the ecological footprint of fishing vessels
Current Biology, 2014Co-Authors: Thomas W Bodey, Stephen C Votier, Keith C Hamer, Samantha C Patrick, Ian R Cleasby, Ewan D Wakefield, Mark Jessopp, Hans D Gerritsen, Stuart BearhopAbstract: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.
Louise Champoux - One of the best experts on this subject based on the ideXlab platform.
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an investigation of physiological effects of the deepwater horizon oil spill on a long distance migratory seabird the Northern Gannet
Marine Pollution Bulletin, 2020Co-Authors: Louise Champoux, Emilie Lacaze, Pauline Brousseau, Jeanfrancois Rail, Keith A Hobson, Magali Houde, Maeva Giraudo, Cynthia D Franci, Graham D Fairhurst, Magella GuillemetteAbstract:Exposure to oil can have long-term impacts on migratory birds. Following the 2010 Deepwater Horizon blowout in the Gulf of Mexico (GOM), we investigated potential impacts of oil exposure on a population of Northern Gannets (Morus bassanus) that breed on Bonaventure Island (Quebec, Canada) and winter in GOM and along the U.S. Atlantic coast (AC). Blood and feather samples were collected from adults previously equipped with geolocators to determine wintering locations. Parent and alkylated polycyclic aromatic hydrocarbons (PAHs); trace metals; stable isotopes of carbon, nitrogen, and hydrogen; and immune, thyroid, steroid, retinoid, and genetic endpoints were measured. PAH and trace metal concentrations did not differ between Gannets using different wintering sites. Feather stable isotope values varied significantly between birds from different wintering locations. Gannets wintering in GOM showed higher feather corticosterone and plasma thyroid hormone levels, which may indicate increased energetic demands and/or greater exposure to environmental stressors.
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polychlorinated dibenzo p dioxins dibenzofurans and flame retardants in Northern Gannet morus bassanus eggs from bonaventure island gulf of st lawrence 1994 2014
Environmental Pollution, 2017Co-Authors: Louise Champoux, Jeanfrancois Rail, Raphael A LavoieAbstract:Northern Gannet (Morus bassanus) eggs from Bonaventure Island, Quebec, Canada, were collected to monitor concentrations of contaminants. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) and non-ortho polychlorinated biphenyls (PCBs) were measured in eggs from 2004 and 2009, and several brominated and nonbrominated flame retardants (FRs) were measured every 2–5 years in eggs from 1994 to 2014. The sum (Σ) concentrations of PCDDs/Fs were significantly lower in 2009 relative to 2004, but the total toxic equivalent concentrations for PCDDs, PCDFs, and PCBs showed no significant differences (196 ng/kg wet weight (ww) in 2004 and 220 ng/kg ww in 2009). The mean ΣFR concentrations decreased significantly between 1994 and 2014, from 58 ng/g ww to 19 ng/g ww. Hexabromocyclododecane (HBCDD) was the principal nonbrominated FR detected in Gannet eggs and ranged from <1.0 ng/g ww to 6.9 ng/g ww. The PCDD/F and nonortho PCB profiles were dominated by 2,3,7,8- tetrachloro-dibenzofuran (2,3,7,8-TCDF; from 26.2 ng/g ww to 34.8 ng/kg ww) and PCB-77 (from 1580 ng/g ww to 2650 ng/kg ww), respectively. Although the values of both ecological tracer stable isotopes of carbon (δ13C) and nitrogen (δ15N) showed differences among the years, no temporal trends were observed, which indicates relatively stable adults' diet and foraging area over this time period. The trends over time in concentrations of the studied contaminants likely reflect a decrease in environmental contamination. The mean 2012 eggshell thickness was 10% lower than the pre-DDT value and corresponded to a year of poor reproductive success.
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temporal trends of mercury organochlorines and pcbs in Northern Gannet morus bassanus eggs from bonaventure island gulf of st lawrence 1969 2009
Environmental Pollution, 2015Co-Authors: Louise Champoux, Jeanfrancois Rail, Raphael A Lavoie, Keith A HobsonAbstract:Since 1969, Northern Gannet (Morus bassanus) eggs from Bonaventure Island, Quebec, have been collected to monitor concentrations of contaminants. Levels of p,p′-DDE, which caused low breeding success of Bonaventure Gannets in the 1960s, decreased by 99.4% from 1969 to 2009 (17.1–0.1 mg/kg ww), with concomitant improvement of hatching success. PCBs, most organochlorines and mercury also showed decreasing trends. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) were measured to track the possible influence of diet changes on concentrations of contaminants over time. The confounding effect of the combustion of fossil fuels on baseline values of δ13C (the Suess effect) was taken into account. No temporal trends were observed in δ13C and δ15N values in Gannet eggs. Hence trophic level or foraging area had a negligible influence on temporal trends of contaminants.
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immunologic and genotoxic profile of Northern Gannet morus bassanus from bonaventure island
Journal of Xenobiotics, 2014Co-Authors: C Brousseaufournier, Emilie Lacaze, Louise Champoux, Michel Fournier, Pauline BrousseauAbstract:The Northern Gannet is the biggest marine bird to nest in the St-Lawrence. The Bonaventure Island colony is one of the most important Gannet colony in the world with about 70% of total North America population.1 However, since a few years that number is lowering. Indeed, the reproductive success of Gannet went from 76% in 1979 to a critical 8% in 2012.2 Thus, the number of nesting couple got lowered by 12,000. Since the Gannets are migratory birds at the top of the food web, they are susceptible to be exposed to a wide variety of stressors and to bioaccumulate pollutants. Thus, Gannets monitoring studies are essential in providing insight into possible environmental damage. We therefore decided to investigate two major biological responses: the immune response and DNA damage. On one hand, the study of the immune system of those birds could allow to pinpoint an explanation to this drastic decrease in their population. On the other hand, DNA damage related to environmental genotoxicants is a crucial point as they can lead to mutations and developmental impairment or cancer occurrence. DNA damage can negatively impact individual organism fitness, reproductive success, and subsequently, population dynamics.3 However, since biomarkers of immunotoxicity and genotoxicity where never applied to the Gannet we had first to demonstrate that these research tools could be used adequately to the Northern Gannet. The immune system of bird is composed of 2 types of defensive pathways: the non-specific immunity and the specific immunity. The nonspecific defense comprises various tools ranging from physical and biochemical barriers, to soluble and cellular components. The cells associated with the non-specific pathway are mainly heterophils (equivalent of mammal’s neutrophils). The specific immunity is based on the antigens recognition and is provided by 2 types of leukocytes which are B and T cells. In our immunologic analysis we focused on the heterophils and their phagocytic capabilities whereas the genotoxicity was evaluated using the Comet assay on erythrocytes.
Raphael A Lavoie - One of the best experts on this subject based on the ideXlab platform.
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polychlorinated dibenzo p dioxins dibenzofurans and flame retardants in Northern Gannet morus bassanus eggs from bonaventure island gulf of st lawrence 1994 2014
Environmental Pollution, 2017Co-Authors: Louise Champoux, Jeanfrancois Rail, Raphael A LavoieAbstract:Northern Gannet (Morus bassanus) eggs from Bonaventure Island, Quebec, Canada, were collected to monitor concentrations of contaminants. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/Fs) and non-ortho polychlorinated biphenyls (PCBs) were measured in eggs from 2004 and 2009, and several brominated and nonbrominated flame retardants (FRs) were measured every 2–5 years in eggs from 1994 to 2014. The sum (Σ) concentrations of PCDDs/Fs were significantly lower in 2009 relative to 2004, but the total toxic equivalent concentrations for PCDDs, PCDFs, and PCBs showed no significant differences (196 ng/kg wet weight (ww) in 2004 and 220 ng/kg ww in 2009). The mean ΣFR concentrations decreased significantly between 1994 and 2014, from 58 ng/g ww to 19 ng/g ww. Hexabromocyclododecane (HBCDD) was the principal nonbrominated FR detected in Gannet eggs and ranged from <1.0 ng/g ww to 6.9 ng/g ww. The PCDD/F and nonortho PCB profiles were dominated by 2,3,7,8- tetrachloro-dibenzofuran (2,3,7,8-TCDF; from 26.2 ng/g ww to 34.8 ng/kg ww) and PCB-77 (from 1580 ng/g ww to 2650 ng/kg ww), respectively. Although the values of both ecological tracer stable isotopes of carbon (δ13C) and nitrogen (δ15N) showed differences among the years, no temporal trends were observed, which indicates relatively stable adults' diet and foraging area over this time period. The trends over time in concentrations of the studied contaminants likely reflect a decrease in environmental contamination. The mean 2012 eggshell thickness was 10% lower than the pre-DDT value and corresponded to a year of poor reproductive success.
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temporal trends of mercury organochlorines and pcbs in Northern Gannet morus bassanus eggs from bonaventure island gulf of st lawrence 1969 2009
Environmental Pollution, 2015Co-Authors: Louise Champoux, Jeanfrancois Rail, Raphael A Lavoie, Keith A HobsonAbstract:Since 1969, Northern Gannet (Morus bassanus) eggs from Bonaventure Island, Quebec, have been collected to monitor concentrations of contaminants. Levels of p,p′-DDE, which caused low breeding success of Bonaventure Gannets in the 1960s, decreased by 99.4% from 1969 to 2009 (17.1–0.1 mg/kg ww), with concomitant improvement of hatching success. PCBs, most organochlorines and mercury also showed decreasing trends. Stable isotopes of carbon (δ13C) and nitrogen (δ15N) were measured to track the possible influence of diet changes on concentrations of contaminants over time. The confounding effect of the combustion of fossil fuels on baseline values of δ13C (the Suess effect) was taken into account. No temporal trends were observed in δ13C and δ15N values in Gannet eggs. Hence trophic level or foraging area had a negligible influence on temporal trends of contaminants.
David Grémillet - One of the best experts on this subject based on the ideXlab platform.
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no way home collapse in Northern Gannet survival rates point to critical marine ecosystem perturbation
Marine Biology, 2020Co-Authors: David Grémillet, Clara Peron, Amelie Lescroel, Jerome Fort, Samantha C Patrick, Besnard Aurelien, Pascal ProvostAbstract:Seabirds are one of the most threatened of all bird groups, with a marked community-wide decline across the last decades. Yet, some seabird species are more resilient than others, and it is essential to study under which conditions even these highly resilient organisms are affected by global changes. Using global location sensors (GLS), demographic and stable isotope analyses, we performed a long-term study of the migration biology and inter-annual survival of Northern Gannets (Morus bassanus) breeding on Rouzic Island in Brittany, France. Across 2006-2015, our analyses showed that the birds spent the inter-breeding period off Western Europe, in the Mediterranean or off West Africa. There were no inter-annual trends in the use of these different areas, but isotopic analyses suggested food competition between Gannets and industrial-scale fisheries. Crucially, we found a precipitous decline in the return rates of birds equipped with GLS, from 90% in 2006-2007 to less than 10% after 2015. This decline was consistent with a marked decrease in inter-annual survival probabilities for ringed adult Gannets, from >90% in 2014-2015 to <60% in 2018-2019, and with a population decline of the Rouzic Gannet breeding colony in recent years. Strong ecological signals provided by Northern Gannets point to critical marine ecosystem perturbation in the Eastern Atlantic, and the decline of this resilient and emblematic species should lead to the urgently needed transformation of marine policies.
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contrasting population trends at seabirds colonies is food limitation a factor in norway
Journal of Ornithology, 2015Co-Authors: Emeline Pettex, Robert T. Barrett, Svein-håkon Lorentsen, David Grémillet, Jean-baptiste Pons, Francesco Bonadonna, Lorien PichegruAbstract:Norwegian Northern Gannet Morus bassanus populations exhibit contrasting trends on a regional scale, with several colony extinctions having occurred in recent decades. In an attempt to understand the ecological drivers of such variability, we tested whether resource availability is a factor limiting the current development of Gannetries in the Lofoten/Vesteralen area. Between 2007 and 2010, we recorded arrival and departure times of breeding Northern Gannets from two colonies from regions showing contrasting population growth rates during the past two decades. We also recorded the duration of joint attendances by Northern Gannet parents at the nest, performed opportunistic diet sampling and counted numbers of occupied nests. Finally, we compiled ring recoveries over a 30-year period to assess inter-colony movements. Norwegian Gannet parents spent more time together, attending their chick, and performed shorter foraging trips than those in British and French colonies of similar size. This suggests that, despite some annual variations, their foraging effort was relatively low. Diet samples from both colonies mainly constituted fish of high energetic value, such as large herring Clupea harengus, mackerel Scomber scombrus, and saithe Pollachius virens, prey that are relatively abundant within the study area. Data from ringed birds revealed a northward movement of adults ringed as breeding birds and chicks from extinct Lofoten colonies that established a growing colony close to the North Cape. Recorded foraging features (trip duration, joint attendance and prey quality) during our study does not indicate food availability as a limiting factor explaining successive extinctions and re-colonisations of breeding sites in Lofoten/Vesteralen. White-tailed Eagles Haliaeetus albicilla are known to predate opportunistically on Northern Gannet adults or chicks and their populations are growing in the Lofoten area. Their potential impact on the Norwegian Northern Gannet population dynamics should be further investigated.
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Multi-scale foraging variability in Northern Gannet (Morus bassanus) fuels potential foraging plasticity
Marine Biology, 2012Co-Authors: Emeline Pettex, Robert T. Barrett, Svein-håkon Lorentsen, David Grémillet, Olivier Gimenez, Jean-baptiste Pons, Céline Bohec, Francesco BonadonnaAbstract:The survival of marine predators depends on behavioural plasticity to cope with changes in prey distribution. Variability in behaviour might predict plasticity and is easier to assess than plasticity. Using miniaturized GPS loggers over several breeding seasons in two Norwegian Northern Gannet ( Morus bassanus ) colonies, we investigated if and how the variability within and between individuals, but also between colonies and years, affected foraging strategies. Results revealed strong individual variability (foraging trip durations, foraging effort and different foraging areas). Individuals from both colonies showed preferred commuting routes, flight bearings and feeding hotspots. Individuals from the largest colony used larger and more foraging areas than individuals from the small colony. Feeding hotspots and foraging ranges varied amongst years in the largest colony only. Our study demonstrated that Gannets show flexibility by changing prey fields that are driven by shifting oceanographic conditions.
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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, 2012Co-Authors: James Grecian, Stuart Bearhop, Keith C Hamer, David Grémillet, Matthew J Witt, Martin J Attrill, Brendan J Godley, Stephen C VotierAbstract: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.
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application of habitat suitability modelling to tracking data of marine animals as a means of analyzing their feeding habitats
Ecological Modelling, 2008Co-Authors: Henrik Skov, Keith C Hamer, David Grémillet, Stefan Garthe, Elizabeth Humphreys, Kerstin Geitner, Janos C Hennicke, Hjalte Parner, Sarah WanlessAbstract:This paper investigates the potential for using quantitative applications of statistical models of habitat suitability based on marine animal tracking data to identify key feeding areas. Presence-only models like Ecological Niche Factor Analysis (ENFA) may be applicable to resolve habitat gradients and potentially project habitat characteristics of tracked animals over large areas of ocean. We tested ENFA on tracking data of the Northern Gannet (Morus bassanus) obtained from the colony at Bass Rock, western North Sea in 2003. A total of 217 diving events were selected for model development. The ecological variables of the model were calibrated by using oceanographic structures with documented influences on seabird distribution, derived from satellite and bathymetric data. The model parameters were estimates of habitat marginality and specialisation computed by comparing the distribution of the Gannet in the multivariate oceanographic space encompassed by the recorded logger data with the whole set of cells in the study area. Marginality was identified by differences to the global mean and specialization was identified by the ratio of species variance to global variance. A habitat suitability index was computed on the basis of the marginality factors and the first four specialisation factors by allocating values to all grid cells in the study area, which were proportional to the distance between their position and the position of the species optimum in the factorial space. Although Gannets were using a large sector of the North Sea for feeding, ENFA estimated high habitat suitability scores within a relatively small coherent zone corresponding to a hydrographic frontal area, located east of the colony. The model was evaluated by using Jack-knife cross-validation and by comparison of the predicted core feeding area with results from historic field surveys. We discuss the limitations and potentials for applying habitat suitability models to tracking data in the marine environment, and conclude that the inclusion of hydrodynamic variables seems to be the biggest constraint. Overcoming this constraint, ENFA provides a promising method for achieving improved models of the distribution of marine species with high research and conservation priority. Due to the better coverage of entire feeding ranges, the limited influence of historic factors and the lack of bias from sampling design, marine animal tracking may provide better data than at-sea surveys for habitat suitability modelling.
Stuart Bearhop - One of the best experts on this subject based on the ideXlab platform.
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sex differences in migration and demography of a wide ranging seabird the Northern Gannet
Marine Ecology Progress Series, 2019Co-Authors: Zoe Deakin, Stuart Bearhop, Thomas W Bodey, Bethany L Clark, James Grecian, Keith C Hamer, Richard B Sherley, Matt Gummery, Jude V Lane, Greg MorganAbstract: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) 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.
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frequency and consequences of individual dietary specialisation in a wide ranging marine predator the Northern Gannet
Marine Ecology Progress Series, 2018Co-Authors: Stephen C Votier, Thomas W Bodey, Keith C Hamer, Samantha C Patrick, Ian R Cleasby, Jason Newton, Ewan D Wakefield, Stuart BearhopAbstract:Individual specialisations in animals are important contributors to a wide range of ecological and evolutionary processes, and have been particularly documented in relation to multiple aspects of foraging behaviours. Central-place foragers, such as seabirds, frequently exhibit pronounced specialisations and individual differences in a variety of foraging traits. In particular, the availability of fisheries discards alongside natural prey resources provides additional potential for differentiation and specialisation for opportunistically scavenging seabird species. However, the consequences of such specialisations for at-sea distributions and intraspecific interactions are not well known. Here, we investigated the links between the degree of dietary specialisation on natural or discarded prey and the foraging movements and spatial occupancy of Northern Gannets Morus bassanus in relation to differing intraspecific competition at 6 colonies of differing sizes. We found that, at most colonies, individuals with different dietary strategies concentrated foraging at differing levels of intraspecific competition. In addition, individuals pursuing different strategies were frequently, but not consistently, spatially separated, distinctions that were most acutely seen in females. However, this variation in individual strategy had no significant impact on current body condition. These analyses demonstrate how foraging-associated metrics need not covary within an unconstrained system. They also reveal that specialisation can have important consequences for the competitive regimes individuals experience, highlighting the complexity of examining interacting consequences at large spatial scales.
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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, 2017Co-Authors: Stephen C Votier, Annette L Fayet, Stuart Bearhop, Thomas W Bodey, Bethany L Clark, James Grecian, Tim Guilford, Keith C Hamer, Jana W E Jeglinski, Greg MorganAbstract:Individual foraging specializations, where individuals use a small component of the population niche width, are widespread in nature with important ecological and evolutionary implications. In long-lived animals, foraging ability develops with age, but we know little about the ontogeny of individuality in foraging. Here we use precision global positioning system (GPS) loggers to examine how individual foraging site fidelity (IFSF), a common component of foraging specialization, varies between breeders, failed breeders and immatures in a long-lived marine predator-the Northern Gannet Morus bassanus Breeders (aged 5+) showed strong IFSF: they had similar routes and were faithful to distal points during successive trips. However, centrally placed immatures (aged 2-3) were far more exploratory and lacked route or foraging site fidelity. Failed breeders were intermediate: some with strong fidelity, others being more exploratory. Individual foraging specializations were previously thought to arise as a function of heritable phenotypic differences or via social transmission. Our results instead suggest a third alternative-in long-lived species foraging sites are learned during exploratory behaviours early in life, which become canalized with age and experience, and refined where possible-the exploration-refinement foraging hypothesis. We speculate similar patterns may be present in other long-lived species and moreover that long periods of immaturity may be a consequence of such memory-based individual foraging strategies.
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seabird movement reveals the ecological footprint of fishing vessels
Current Biology, 2014Co-Authors: Thomas W Bodey, Stephen C Votier, Keith C Hamer, Samantha C Patrick, Ian R Cleasby, Ewan D Wakefield, Mark Jessopp, Hans D Gerritsen, Stuart BearhopAbstract: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.
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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, 2012Co-Authors: James Grecian, Stuart Bearhop, Keith C Hamer, David Grémillet, Matthew J Witt, Martin J Attrill, Brendan J Godley, Stephen C VotierAbstract: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.