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Many established models of animal foraging assume that individuals are ecologically equivalent. However, it is increasingly recognized that populations may comprise individuals who differ consistently in their diets and foraging behaviors. For example, recent studies have shown that individual foraging site fidelity (IFSF, when individuals consistently forage in only a small part of their population's home range) occurs in some colonial breeders. Short-term IFSF could result from animals using a win--stay, lose--shift foraging strategy. Alternatively, it may be a consequence of individual specialization. Pelagic seabirds are colonial central-place foragers, classically assumed to use flexible foraging strategies to target widely dispersed, spatiotemporally patchy prey. However, tracking has shown that IFSF occurs in many seabirds, although it is not known whether this persists across years. To test for long-term IFSF and to examine alternative hypotheses concerning its cause, we repeatedly tracked 55 Northern Gannets (Morus bassanus) from a large colony in the North Sea within and across three successive breeding seasons. Gannets foraged in neritic waters, predictably structured by tidal mixing and thermal stratification, but subject to stochastic, wind-induced overturning. Both within and across years, coarse to mesoscale (tens of kilometers) IFSF was significant but not absolute, and foraging birds departed the colony in individually consistent directions. Carbon stable isotope ratios in gannet blood tissues were repeatable within years and nitrogen ratios were also repeatable across years, suggesting long-term individual dietary specialization. Individuals were also consistent across years in habitat use with respect to relative sea surface temperature and in some dive metrics, yet none of these factors accounted for IFSF. Moreover, at the scale of weeks, IFSF did not decay over time and the magnitude of IFSF across years was similar to that within years, suggesting that IFSF is not primarily the result of win--stay, lose--shift foraging. Rather, we hypothesize that site familiarity, accrued early in life, causes IFSF by canalizing subsequent foraging decisions. Evidence from this and other studies suggests that IFSF may be common in colonial central-place foragers, with farreaching consequences for our attempts to understand and conserve these animals in a rapidly changing environment. [ABSTRACT FROM AUTHOR]

Two unconnected time-integrated tracers of niche use provided similar conclusions about individual foraging behaviour and niche adaptations (functional traits in head shape) within a subarctic lake population of Arctic charr ( Salvelinus alpinus). Zooplanktivorous individuals mainly from the pelagic zone were characterised by having low δ13C values, high infections of the parasites transmitted by pelagic copepods (especially Diphyllobothrium spp.) and slender heads with long snouts. In contrast, fish individuals that had consumed benthic prey in the littoral zone were enriched in δ13C and had high abundances of parasites transmitted by Gammarus lacustris ( Cyathocephalus truncatus and Cystidicola farionis) and a robust head shape. There were strong positive correlations between individual δ13C values and the abundance of the two parasite species transmitted by Gammarus, but a negative correlation between δ13C and the infection of copepod-borne parasites. The close relationships between diet variation (foraging behaviour), the time-integrated ecological tracers ( SI and parasites) and functional trophic morphology (niche adaptations) evidently reflect long-term temporally stable niche use of each individual predator. The two independent time-integrated tracers both gave valuable information of specialised trophic behaviour at the individual level, which is an important basis for studies related to ecological (e.g., resource partitioning) and evolutionary (e.g., polymorphism) topics within a population. [ABSTRACT FROM AUTHOR]

Aim Demographic linkage between subpopulations plays a critical role in population processes. Metapopulation dynamics, however, remains one of the most poorly understood aspects of population biology. This is especially true for small, pelagic seabirds because their discrete subpopulations are located on offshore islands, separated by vast areas of open ocean, making monitoring logistically challenging. Seabird populations often contain large numbers of immature pre-breeders that may be important for subpopulation connectivity and demography, but are poorly studied. Here we provide evidence for intercolony movement of pre-breeding Leach's storm-petrels Oceanodroma leucorhoa among three colonies spanning the North Atlantic Ocean. We discuss their influence on metapopulation dynamics and the extinction risk of a subpopulation under threat from extreme predation. Location North Atlantic Ocean Islands ( Scotland, Canada & Iceland). Methods We use a novel application of Bayesian stable isotope mixing models to infer recent movement of pre-breeding birds between three major breeding populations in the North Atlantic. Carbon and nitrogen stable isotope values from breeding birds (central place foragers) sampled at each colony were used as model sources and pre-breeding birds as model mixtures. Results Of 134 pre-breeding Leach's storm-petrels sampled at three colonies across the North Atlantic, five had isotope mixing model estimates dissimilar (< 25%) to their colony of capture and were instead isotopically similar to another breeding region. Nineteen further pre-breeders had highly mixed signatures (< 50% for the colony of capture), indicating possible recent movement between colonies. Main conclusions Our findings provide evidence for interpopulation connectivity of pre-breeding Leach's storm-petrels among colonies spanning the North Atlantic. These results highlight the significance of cryptic young age-classes in metapopulation dynamics and the demographic processes. Moreover, they provide us with a better understanding of how one subpopulation remains extant, despite experiencing extreme predation rates. [ABSTRACT FROM AUTHOR]

CapsuleStable isotope composition of feathers grown in Africa indicates that Willow Warblers,Phylloscopus trochilus, breeding in areas of Britain experiencing different population trends may vary in their distribution, timing of moult and/or use of prey resources during the non-breeding season. AimsTo compare stable isotope ratios of feathers of Willow Warblers breeding in parts of Britain with differing rates of population change. MethodsFeathers were collected from three regions with differing recent population trends; northern Scotland (population increased), western Wales (declined slightly) and eastern England (declined rapidly). Collection occurred at ringing sites run by British Trust for Ornithology (BTO) volunteers as part of the Constant Effort Sites (CES) scheme between April and July in 2008 and 2009. ResultsWillow Warblers from northern Scotland had significantly higherδ15N andδ13C values than those from eastern England, although the regional mean values did not differ greatly. There was no significant difference inδ15N andδ13C values between the sexes, butδ15N values were significantly greater in individuals caught later in the breeding season. ConclusionsDuring the premigratory moult period in Africa, Willow Warblers from different parts of Britain may vary in their distribution, timing of moult and/or use of prey resources. [ABSTRACT FROM AUTHOR]

Natural populations often vary in their degree of ecological, morphological and genetic divergence. This variation can be arranged along an ecological speciation continuum of increasingly discrete variation, with high inter-individual variation at one end and well defined species in the other. In postglacial fishes, evolutionary divergence has commonly resulted in the co-occurrence of a pelagic and a benthic specialist. We studied three replicate lakes supporting sympatric pelagic and benthic European whitefish ( Coregonus lavaretus (L.)) morphs in search for early signs of possible further divergence into more specialized niches. Using stomach content data (recent diet) and stable isotope analyses (time-integrated measure of trophic niche use), we observed a split in the trophic niche within the benthic whitefish morph, with individuals specializing on either littoral or profundal resources. This divergence in resource use was accompanied by small but significant differences in an adaptive morphological trait (gill raker number) and significant genetic differences between fish exploiting littoral and profundal habitats and foraging resources. The same pattern of parallel divergence was found in all three lakes, suggesting similar natural selection pressures driving and/or maintaining the divergence. The two levels of divergence (a clear and robust benthic - pelagic and a more subtle littoral - profundal divergence) observed in this study apparently represent different stages in the process of ecological speciation. [ABSTRACT FROM AUTHOR]

Rivers in urban locations frequently receive contaminated wastewater and particulate waste either directly from storm overflows or from sewage treatment facilities. Although many urban streams are now recovering from wide-scale historic pollution, lower-level effects on water chemistry, nutrients and biotic composition are still widespread. We aimed to determine whether such effects could be detected using stable isotope ratios (δN, δC and δS) in macroinvertebrates alone or in conjunction with traditional biomonitoring. Macroinvertebrates were collected upstream and downstream of 11 different secondary wastewater treatment works (WwTW) in South Wales and the Welsh borders (United Kingdom). Overall, mean invertebrate δN signatures downstream of the WwTW were significantly enriched despite variation amongst sites. Moreover, changes between upstream and downstream macroinvertebrate δN values were highly correlated with patterns in macroinvertebrate community composition, increased total macroinvertebrate abundance, and reduced Shannon Diversity and other biomonitoring indices (% EPT, % shredders and ASPT scores). Changes in invertebrate δN values also paralleled the consented discharge volumes and population equivalents from each WwTW. In contrast, isotopic ratios of δC and δS were unable to distinguish or quantify wastewater input into the rivers but differences were apparent amongst study streams. Overall, these results suggest that macroinvertebrate δN signatures can detect and quantify the effects of secondary sewage treatment inputs to riverine ecosystems. Moreover, the method potentially provides a sensitive means for tracing sewage-derived nutrients into food webs while inferring effects on aquatic communities where sewage-loads are subtle or confounded by other stressors. [ABSTRACT FROM AUTHOR]

Epidermal skin samples from eastern North Atlantic killer whales, Orcinus orca, were analyzed for carbon and nitrogen stable isotope ratios. From those, comparisons within a data set of 17 samples collected from Tysfjord, Norway, in November suggested that diet is relatively specialized during this time period at this location. There were significant differences between a small set of samples from Iceland and those collected from Norway, which had all been assigned to the same population by a previous population genetics study. The results would be consistent with matrilines feeding on either the Norwegian or Icelandic stocks of Atlantic herring ( Clupea harengus). There was no significant difference within Icelandic samples between those assigned to the population known to feed upon herring and those assigned to a population hypothesized to follow Atlantic mackerel ( Scomber scombrus). The greatest differences were between the epidermal samples analyzed in this study and tooth and bone collagen samples from the North Sea that were analyzed previously, which also showed significantly more variation in isotopic ratios than found for skin samples. These differences could reflect differences in turnover rate, differences in diet-tissue fractionation and discrimination due to the amino acid composition of the different tissues, and/or greater competition promoting dietary variation between groups in the North Sea. [ABSTRACT FROM AUTHOR]

How individuals colonising novel environments overcome the diverse suite of new selection pressures is a fundamental question in ecology and evolution. Urban environments differ markedly from the rural ones that they replace and successful colonisation of urban areas may therefore require local adaptation and phenotypic/genetic divergence from ancestral populations. Such a process would be facilitated by limited dispersal to and from the novel habitat. Here we assess divergence in migratory behaviour between seven pairs of urban and rural European blackbird Turdus merula populations along a 2800 km transect across Europe. This former forest specialist is now amongst the most abundant urban birds across most of its range. We use a stable isotope approach due to the lack of sufficient ringing data from multiple urban populations, and compare hydrogen isotopic ratios of tissues grown in the breeding (feathers) and wintering areas (claws) to derive an index of long distance migratory behaviour. We find a tendency for urban blackbirds to be more sedentary than rural ones at all sites and this divergence is particularly strong at the north-eastern limit of our transect, i.e. in Estonia and Latvia. These urban populations are those that have been established most recently (from the late 1930s to 1950s) implying that urbanisation can promote rapid ecological divergence. The increased sedentary behaviour of urban birds could promote further ecological divergence between rural and urban populations, such as the earlier breeding of urban blackbirds, and in some cases may contribute to their previously documented genetic divergence. [ABSTRACT FROM AUTHOR]

Capsule The 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. Aims To evaluate if Robins in Iberia are displaced from their nesting areas by the presence of large numbers of competitors originating from higher latitudes. Methods Data 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 (δ2H) in feathers, and sex ratios determined through molecular techniques, allowed an insight into the numerical importance of invading Robins from higher latitudes. Results Robins 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. δ2H 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. Conclusion Despite the occupation of their range by migrants, local birds are largely sedentary. [ABSTRACT FROM AUTHOR]

The article discusses a research study which found the influence of winter habitat in the number of feather mites of two species living on European robins Erithacus Rubecula. Study results show the difference in the Proctophyllodes rubeculinus and Trouessartia c.f. rubecula loads of migrant European robins depending on the winter habitat they occupy. The researchers observed the increased abundance of mites as winter progressed and they found that ventral and dorsal mite loads had no effect on muscle or fat scores of the robins.

The article discusses a research study on phenotypic variation and migratory dichotomy of marine turtles. Researchers satellite-tracked regions of 18 migratory loggerhead sea turtles Caretta caretta to determine the relationship between inferred migratory strategies and fitness correlates where 10 turtles moved north to foraging areas in the Adriatic Sea while 8 moved south to forage in the coast of North Africa. Results showed that female turtles foraging in the north were larger that those foraging in the south. Findings on the combination of stable isotope signatures and satellite tracking indicated the possibility of scaling up knowledge from electronic tracking of sea turtles.

The article discusses a study on the Eagle Owls Bubo bubo, a legitimate native birds of Great Britain. Based on fossils and archaeological findings, Eagle Owls have existed in Britain for 700,000 years up to the last Ice Age. In 1997, the birds were taken off the British List of indigenous animals on the basis that no Eagle Owl has been found to be existing in the British wilds for the past 200 years. It is noted that the discovery of breeding pairs in Yorkshire and Lancashire re-ignites the question of the Eagle Owl's origins.

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 FROM AUTHOR]