Herring Gulls Larus Argentatus Research Articles

New Insights on Polar Bear (<i>Ursus maritimus</i>) Diet from Faeces based on Next-Generation Sequencing Technologies

Practical tools to quantify range-wide dietary choices of the polar bear have not been well developed, thus impeding the monitoring of this species in a changing climate. Here we describe our steps toward non-invasive polar bear diet determination with the optimization of 454 pyrosequencing of a 136 base pair (bp) mitochondrial cytochrome b (cytb) fragment amplified from the extracts of captive and wild polar bear faeces. We first determine the efficacy, reliability, and accuracy of our method using five faecal samples from a captive polar bear fed a known diet at the Canadian Polar Bear Habitat in Cochrane, Ontario, Canada; 19 samples from three polar bears at the Metro Toronto Zoo, Toronto, Ontario, Canada; and seven samples from seven wild (unfed) polar bears from a holding facility in Churchill, Manitoba, Canada. We report 91% overall success in amplifying a 136 bp cytb amplicon from the faeces of polar bears. Our DNA analyses accurately recovered the vertebrate diet profiles of captive bears fed known diets. We then characterized multiyear vertebrate prey diet choices from free-ranging polar bears from the sea ice of the M’Clintock Channel polar bear management unit, Nunavut, Canada (n = 117 from an unknown number of bears). These data point to a diet unsurprisingly dominated by ringed seal (Pusa hispida) while including evidence of bearded seal (Erignathus barbatus), harbour seal (Phoca vitulina), muskox (Ovibos moschatus ssp.), Arctic fox (Vulpes lagopus), wolf (Canis lupus), Herring Gull (Larus argentatus), and Willow Ptarmigan (Lagopus lagopus). We found low levels of contamination (< 3% of sequences when present) and suggest specific process improvements to reduce contamination in range-wide studies. Together, these findings indicate that next-generation sequencing-based diet assessments show great promise in monitoring free-ranging polar bears in this time of climate change. 

COVID-19 lockdown reveals tourists as seabird guardians

The widespread lockdowns put in place to limit the spread of the new coronavirus disease (COVID-19) offers a rare opportunity in understanding how human presence influence ecosystems. Using data from long-term seabird monitoring, we reveal a previously concealed guarding effect by tourist groups on an iconic seabird colony in the Baltic Sea. The absence of tourists in 2020 lead to a sevenfold increase in presence of white-tailed eagles Haliaeetus albicilla, a sevenfold increase in their disturbance of breeding common murres Uria aalge and causing 26% lower murre productivity than the long-term average. Eagles did not prey on murres, but their frequent disturbances delayed egg laying and facilitated egg predation from herring gulls Larus argentatus and hooded crows Corvus cornix. Based on our findings, we suggest that human presence could be used as a strategic measure in guarding seabird colonies, and that a social-ecological systems perspective is vital for long-term success in protected area management.

Opportunistic predation of birds by breeding Herring Gulls (Larus argentatus).

Dietary specialization, exploiting a small fraction of available food resources, is commonly reported for gulls and skuas. Predation of birds by these species is usually considered a specialist strategy employed by the minority of the population but non-specialists also predate birds and may actually have a greater impact on the prey species. To date, most studies have focused on predatory bird-specialists, down-playing the possible importance of opportunistic predation by non-specialists. We addressed this by studying diet (regurgitated pellets and prey remains) and behavior of breeding Herring Gulls (Larus argentatus) over three summers at Gull Island, a mixed-species breeding colony in Lake Ontario. One-third of all pellets analyzed contained bird remains, primarily the most numerous breeding bird: Ring-billed Gull (L. delawarensis) chicks (51%) and adults (36%). Although all but one pair of Herring Gulls ate birds, all pairs maintained broad and mostly similar diets, with birds accounting for at most one-third of prey. Behavior also indicated that Herring Gulls at Gull Island were not predatory bird-specialists because predation was too infrequent to meet energetic requirements, was largely unsuccessful and was only ever observed when Ring-billed Gulls strayed into Herring Gull breeding territories. Instead, bird predation appeared mainly opportunistic, increasing with seasonal availability, access to shoreline, proximity to nesting Ring-billed Gulls and breeding territory size. Compared with predatory specialist Herring Gulls in the same region, individuals that predated birds at Gull Island did not display specialist behaviors and killed six times fewer birds (0.1–0.4 per day, on average) but were over 20 times more numerous (98% of the population versus 4%). Thus, our results indicate that opportunistic predation by non-specialists may have important consequences for prey species. Since opportunistic predation cannot be effectively managed using techniques widely advocated for specialist predators, it is essential to investigate cause of predation by large gulls prior to lethal management.

Preen oil chemical composition in herring gull Larus argentatus, common gull Larus canus and black-headed gull Chroicocephalus ridibundus confirms their status as two separate genera

Fatty acid and alcohol components of preen oil were determined in three gull species that belong to two systematic genera: herring gull Larus argentatus, common gull Larus canus and black-headed gull Chroicocephalus ridibundus. All gulls were captured in winter, in Gdańsk, Poland. All gulls produced monoesters composed of C7–C16 saturated fatty acids and C11–C20 saturated alcohols, with n-octanoic acid and n-hexadecanol as the major fatty acid and alcohol, respectively. Preen oils of black-headed gull had higher content of trimethyl fatty acids, 2,8-dimethylundecanoic acid, 2,6-dimethylundecanoic acid and 2,6-dimethylnonanoic acid, and lower content of 2-methyl fatty acids than oils of herring gull and common gull. Preen oils produced by black-headed gull also had lower content of 2-methyl alcohols. The relative contents of n-octanoic acid and n-hexadecanol did not differ among species. The differences among species are probably not a result of different diet, as all gulls fed mainly on household refuse. Hence, preen oil analysis confirmed the taxonomic relations among these gull species, that recently were placed into two different genera.

Landscape‐mediated variation in diet is associated with egg size and maculation in a generalist forager

Human impacts alter landscapes with consequences for the distribution and availability of high‐quality food resources to populations inhabiting those landscapes, which may impact on the reproductive output of individuals in those populations. The sensitivity of wild populations to changes in food resources may vary among stages of the annual cycle. For example, in birds, effects are likely to be greater during costly stages such as egg production. Here we compare assimilated diet (from stable isotope analysis of chick feathers) and egg traits (egg size, shape, eggshell colour and maculation, using pattern‐analysis software) in Herring GullsLarus argentatus, across seven colonies in southwest Scotland and Northern Ireland. The Herring Gull is an opportunistic, generalist forager on both marine and terrestrial resources which frequently exploits anthropogenic food sources such as fishery discards and human refuse. We found that larger eggs were laid in colonies where females consumed either a higher proportion of marine resources or terrestrial resources; smaller eggs were laid in colonies where females had an intermediate diet. In colonies where females consumed more marine items, they also laid eggs with higher maculation (intensity and size of spots) compared with colonies where females mainly consumed terrestrial food. We also found smaller and more pointed eggs, suggestive of resource shortages, in larger colonies. Generalist foragers are often thought to have the capacity to buffer themselves against changes in the food web, provided that enough alternative food is available. However, this study highlights that specializing on the most profitable or available resources has consequences for egg traits even in an opportunistic generalist forager exploiting a large range of habitats. If variation in egg traits is related to reproductive output, then understanding the impact of assimilated diet on reproduction early in the breeding season can provide important insights into how populations will respond to landscapes altered by human impact.

Foraging for high caloric anthropogenic prey is energetically costly

BackgroundSeveral generalist species benefit from food provided by human activities. Food from anthropogenic sources is often high in caloric value and can positively influence reproductive success or survival. However, this type of resource may require specific foraging skills and habitat experience with related costs and benefits. As a result, not all individuals utilize these resources equally, with some individuals preferentially foraging in habitats where natural resources of lower energy content are predominant, possibly due to lower energy expenditure of the specific foraging strategy.MethodsHere we investigate whether foraging in habitats which contain high caloric resources of anthropogenic origin is energetically costlier than foraging in habitats with low caloric resources such as intertidal areas or agricultural and natural areas, for example due to increased flight costs, in a generalist seabird, the herring gull Larus argentatus. We use data from GPS trackers with tri-axial acceleration measurements that allow us to quantify time-energy budgets, representing energy expenditure during foraging trips of herring gulls for each habitat.ResultsWe show that the rate of energy expenditure is on average 34% higher when individuals forage for high caloric prey in marine and urban areas compared to foraging for low caloric prey in intertidal and agricultural areas. Energetic estimates suggest that if birds would feed completely on these resources, they have to gather ~ 400 kJ per day more to compensate for the higher foraging costs.ConclusionsEnergy expenditure differs among foraging habitat and may thereby influence foraging decisions of individual herring gulls. As management of anthropogenic resources changes, so too may the costs and potential benefits of foraging strategies which are strongly tied to human activities.

Observations of a novel predatory gull behavior on an invasive ascidian: A new consequence of coastal urban sprawl?

Coastal urbanization has a dramatic effect on both terrestrial and marine ecosystems, altering resources such as food or space. Many species have shifted their ranges in response to anthropogenic pressures, resulting in novel species interactions. Here, we report an observation of a novel foraging behavior of the European Herring Gull (Larus argentatus): the capture and consumption of the widespread sea squirt Ciona intestinalis from under floating pontoons in a recreational marina in Ireland. Multiple gulls were observed performing a complex, multi‐step manipulation of several C. intestinalis individuals to remove their cellulose‐based tunic, which remained unconsumed. Further avenues of investigation are discussed, and hypotheses concerning possible ecosystem effects of novel ecological interactions occurring in proliferating artificial environments are presented.

Individual differences in foraging site fidelity are not related to time‐activity budgets in Herring Gulls

Many populations consist of individuals that differ consistently in their foraging behaviour through resource or foraging site selection. Foraging site fidelity has been reported in several seabird species as a common phenomenon. It is considered especially beneficial in spatially and/or temporally predictable environments in which fidelity is thought to increase energy intake, thereby affecting time‐energy budgets. However, the consequences for activity and energy budget have not been adequately tested. In this paper, we studied the consequences of fine‐scale foraging site fidelity in adult Herring Gulls Larus argentatus in a highly predictable foraging environment with distinct foraging patches. We measured their time‐activity budgets using GPS tracking and tri‐axial acceleration measurements, which also made it possible to estimate energy expenditure. Individual variation in foraging site fidelity was high, some individuals spending most of their time on a single foraging patch and others spending the same amount of time in up to 21 patches. While time and activity budgets differed between individuals, we found no clear relationship with foraging site fidelity. We did find a relationship between the size of the birds and the level of site fidelity; faithful birds tend to have a larger body size. Although differences in foraging time and habitat use between individuals could play a role in the results of the current study, short‐term consequences of variation in foraging site fidelity within a population remain elusive, even when focusing on individuals with a similar foraging specialization (Blue Mussels Mytilus edulis). Studying individuals over multiple years and under varying environmental conditions may provide better insight into the consequences and plasticity of foraging site fidelity.

Intercolony variations in movement patterns and foraging behaviors among herring gulls (Larus argentatus) breeding in the eastern Wadden Sea.

Herring gulls (Larus argentatus) are opportunistic predators that prefer to forage in the intertidal zone, but an increasing degree of terrestrial foraging has recently been observed. We therefore aimed to analyze the factors influencing foraging behavior and diet composition in the German Wadden Sea. Gulls from three breeding colonies on islands at different distances from the mainland were equipped with GPS data loggers during the incubation seasons in 2012–2015. Logger data were analyzed for 37 individuals, including 1,115 foraging trips. Herring gulls breeding on the island furthest from the mainland had shorter trips (mean total distance = 12.3 km; mean maximum distance = 4.2 km) and preferred to feed on the tidal flats close to the colony, mainly feeding on common cockles (Cerastoderma edule) and shore crabs (Carcinus maenas). In contrast, herring gulls breeding close to the mainland carried out trips with a mean total distance of 26.7 km (mean maximum distance = 9.2 km). These gulls fed on the neobiotic razor clams (Ensis leei) in the intertidal zone, and a larger proportion of time was spent in distant terrestrial habitats on the mainland, feeding on earthworms. δ 13C and δ 15N values were higher at the colony furthest from the mainland and confirmed a geographical gradient in foraging strategy. Analyses of logger data, pellets, and stable isotopes revealed that herring gulls preferred to forage in intertidal habitats close to the breeding colony, but shifted to terrestrial habitats on the mainland as the tide rose and during the daytime. Reduced prey availability in the vicinity of the breeding colony might force herring gulls to switch to feed on razor clams in the intertidal zone or to use distant terrestrial habitats. Herring gulls may thus act as an indicator for the state of the intertidal system close to their breeding colony.

The influence of avian biovectors on mercury speciation in a bog ecosystem

Methylmercury (MeHg) is a neurotoxin and endocrine disruptor that bioaccumulates and biomagnifies through trophic levels, resulting in potentially hazardous concentrations. Although wetlands are known hotspots for mercury (Hg) methylation, the effects of avian biovectors on these processes are poorly understood. We examined Hg speciation and distribution in shallow groundwater and surface water from a raised-bog with over 30years of avian biovector (herring gulls Larus argentatus and great black-backed gulls Larus marinus) colonization and guano input. Compared to the reference site, the avian-impacted bog had elevated concentrations of total dissolved organic carbon (TOC), total Hg, MeHg, phosphate (PO43−), and other trace metals, notably Pb, As, Cd and Ni. Spatial interpolation showed that the densest area of gull nesting was co-located with areas that had the highest concentrations of PO43−, MeHg, As and Cd, but not total mercury (THg), and models suggested that Mn, PO43−, and dissolved TOC were strong predictors of MeHg. Our findings suggest that while these gulls may not be a significant source of Hg, the excess of PO43− (a well recognised component of guano) and the subsequent changes in water chemistry due to avian biovector subsidies may increase net Hg methylation.

Can Marsh HarrierCircus aeruginosusprey on Great BustardOtis tarda?

Predator-prey interaction is one of the hottest subjects to study in ecology and many researchers have become interested in this subject. There is little information on feeding habits of birds of prey in the Middle East. In early January 2017, we recorded a Marsh Harrier Circus aeruginosus on a dead Great Bustard Otis tarda in NW Iran. The Great Bustard has not yet been listed in the prey list of the Marsh Harrier. According to literature, the Marsh Harrier occasionally hunts on large birds such as Herring Gull Larus argentatus and geese in Northern Europe. We observed the Marsh Harrier on a dead Great Bustard thinking about whether the former could have killed the latter. Both species are protected by the Department of Environment in Iran, and the Great Bustard is ‘Vulnerable’ in the IUCN Red List.

Post mortem findings and their relation to AA amyloidosis in free-ranging Herring gulls (Larus argentatus).

Since the late 1990s, high mortality and declining populations have been reported among sea birds including Herring gulls (Larus argentatus) from the Baltic Sea area in Northern Europe. Repeated BoNT type C/D botulism outbreaks have occurred, but it remains unclear whether this is the sole and primary cause of mortality. Thiamine deficiency has also been suggested as a causal or contributing factor. With this study, we aimed to investigate gross and microscopic pathology in Herring gulls from affected breeding sites in Sweden in search of contributing diseases. Herring gulls from Iceland served as controls. Necropsies and histopathology were performed on 75 birds, of which 12 showed signs of disease at the time of necropsy. Parasites of various classes and tissues were commonly observed independent of host age, e.g. oesophageal capillariosis and nematode infection in the proventriculus and gizzard with severe inflammation, air sac larid pentastomes and bursal trematodiasis in pre-fledglings. Gross and microscopic findings are described. Notably, amyloidosis was diagnosed in 93 and 33% of the adult birds from Sweden and Iceland, respectively (p<0.001), with more pronounced deposits in Swedish birds (p<0.001). Gastrointestinal deposits were observed in the walls of arteries or arterioles, and occasionally in villi near the mucosal surface. Amyloid was identified within the intestinal lumen in one severely affected gull suggesting the possibility of oral seeding and the existence of a primed state as previously described in some mammals and chickens. This could speculatively explain the high occurrence and previously reported rapid onset of amyloidosis upon inflammation or captivity in Herring gulls. Amyloid-induced malabsorbtion is also a possibility. The Herring gull SAA/AA protein sequence was shown to be highly conserved but differed at the N-terminus from other avian species.

Flock-fishing deep-diving piscivores (Great Crested Grebe Podiceps cristatus, Great Cormorant Phalacrocorax carbo, Common Merganser Mergus merganser) at Lake Vombsjön, southern Sweden, and those that exploit them

Lake Vombsjön in southern Sweden is visited by large numbers of Great Crested Grebes Podiceps cristatus (&gt;2000), Great Cormorants Phalacrocorax carbo (sometimes &gt;1000) and Common Mergansers Mergus merganser (up to 2000) in late autumn and early winter. Different species exploit them. Great Crested Grebes are used especially by commensal Common Gulls Larus canus; the gulls take advantage of fish that flee towards the surface. Common Gulls also use cormorants and mergansers in the same way but also try to kleptoparasitize them. Both Herring Gulls Larus argentatus and Great Black-backed Gulls Larus marinus kleptoparasitize these two species, while Red Kites Milvus milvus, Grey Herons Ardea cinerea and Carrion Crows Corvus corone use them commensally. White-tailed Eagles Haliaeetus albicilla seem to use both methods to obtain fish. On 50% of one hundred visits during November to March, eagles were seen flying low over the fishing flocks. They would fly a metre or so above the flocks and then accelerate and attack a bird holding a fish. The bird would then either try to escape by a rush or by diving, dropping the fish which the eagle seized. Interestingly, the flock-fishing birds showed no fear reactions towards the eagles but appeared to regard them similarly to large gulls.

Dietary Niche Shifts of Multiple Marine Predators under Varying Prey Availability on the Northeast Newfoundland Coast

Understanding species interactions among top marine predators and interactions with their prey can provide important insight into community-level responses to changing prey availability and the role of apex predators as indicators of ecosystem change. On the northeast Newfoundland coast, marine predators rely on capelin (Mallotus villosus), a dominant forage fish, as a food source. Capelin migrate into coastal regions to spawn during July, essentially transforming food supply from low during early summer (i.e. pre-spawning) to high later in the summer (i.e. spawning). During July-August, 2016, we used stable isotopic ratios of nitrogen (δ15N) and carbon (δ13C) to investigate shifts in dietary niche metrics at the predator group-level (trophic position, dietary niche breadth) and community-level (niche overlap, trophic diversity) for multiple marine predators under varying capelin availability. Predator groups included non-breeding shearwaters (great shearwater Ardenna gravis, sooty shearwater A. grisea), humpback whales (Megaptera novaeangliae), and gull chicks (herring gull Larus argentatus, great black-backed gull L. marinus). We also tested the sensitivity of community-level dietary metrics to a variety of published trophic discrimination factors. Tissue samples from shearwaters (blood cellular component), gull chicks (whole blood), and whales (skin), representing average diets over 2-3 weeks, were collected during three periods (early, mid, late) corresponding to increasing capelin availability. Isotopic niche breadth (Standard Ellipse Area, SEAb) narrowed and trophic position shifted toward higher δ15N for all predator groups as capelin availability increased, suggesting a higher reliance on capelin. Trophic diversity (distance to centroid) decreased with increased capelin availability, while pairwise niche overlap between predator groups was highly variable and sensitive to varying trophic discrimination factors. Findings suggest that although capelin is the dominant forage fish during the summer, predators rely on capelin as prey to varying degrees. Combining species- and community-level metrics of dietary niche and trophic diversity may provide a more complete picture of predator responses to prey availability and, thus, may be important monitoring tools to indicate changes in the food supply of marine predators.

Population trends and status of four seabird species (Uria aalge, Alca torda, Larus fuscus, Larus argentatus) at Stora Karlsö in the Baltic Sea

The island of Stora Karlsö hosts the largest colonies of fish-eating seabirds in the Baltic Sea. However, recent and reliable estimates of the number of breeding pairs of the main species have been missing. Based on a complete census in 2014, we estimated the number of Common Guillemots Uria aalge to 15,700 pairs, more than half (up to 70%) of the Baltic Sea population. The number has almost tripled since the early 1970s and the increase has been particularly strong the last 11 years, with an annual increase of 5.1%. We counted 24,600 individual adult Razorbills Alca torda and estimated it to correspond to a maximum of 12,300 pairs in 2015–2016 (census over two seasons). The colony has grown strongly; on average by 5.6% annually since the early 1970s, and Stora Karlsö now hosts up to 30% of the Baltic Sea population. Stora Karlsö also hosts colonies with about 300 pairs each of Lesser Black-backed Gull Larus fuscus and Herring Gull Larus argentatus. The gulls’ trends are negative, with an average annual decline the last 10-year period by 5.0% and 6.2%, respectively.

British Ornithologists’ Union Godman Salvin Prize

Pat's research has addressed an impressively broad range of questions emanating from her core interest in understanding the causes and consequences of life-history trade-offs and resulting life-history variation. She has provided ground-breaking and much needed insights into key physiological and genetic mechanisms that underlie life-history variation, and is unusual in the degree to which she has retained a clear-sighted view and commitment to injecting her research into applied ecology and conservation policy. Although Pat's studies have involved insects, amphibians, fish and mammals, birds have proved an ideal model for addressing her questions of interest, and so ornithology is her natural home. After graduating in Zoology at the University of Glasgow in 1973, Pat moved to Durham undertake a PhD on Herring Gull Larus argentatus ecology, supervised by John Coulson (awarded the Goldman Salvin Prize in 1992). She then returned to a Lectureship in Glasgow, and through the rest of her career has played a pivotal role in the development of ornithological science in Glasgow, the UK and beyond. Pat's early research continued to focus on seabird ecology, with a developing emphasis on interdisciplinary studies into issues such as disease transmission by wintering gulls. These studies continued through the 1980s, including research on emerging conservation issues that showed that seabird declines were being driven by reductions in the local availability of their sandeel prey. Those studies in Shetland illustrate a theme that has underpinned much of Pat's subsequent work, where she has successfully demonstrated fitness consequences of the varied responses that different animals have to environmental change. Building upon those field studies, in which environmental variation provided her with natural experiments, Pat identified a series of systems where experimental manipulations could be used on wild populations. This led to investigations into the constraints on maternal investment, and how maternal condition influenced egg quality, sex ratios and offspring fitness. Her interest in the longer-term consequences of variation in early condition led Pat to develop increasingly elegant experiments with laboratory species such as Zebra Finches Taeniopygia guttata. Collaborating with a diverse group of modellers, physiologists and molecular biologists, these laboratory studies have revealed how early growth conditions, relating both to nutrition and social environments, can influence a range of biological characteristics in later life. Alongside this work on captive species, she has successfully identified opportunities to explore these questions in wild populations, collaborating with colleagues such as previous Goldman Salvin medallists Mike Harris and Sarah Wanless, and further demonstrating the value of the long-term individual-based studies of seabirds on the Isle of May. Together, these studies highlight how Pat has used ornithology to address fundamental questions of broad biological interest. Yet at the same time, she retains an active research interest in avian conservation, particularly in the way that she has driven the science underpinning the Scottish Chough Study Group's major impact on current conservation strategies for this species. Pat's research has resulted in over 200 scientific papers and contributions to many books and popular science articles. Her work is highly cited, and has had an important influence across ornithology and other disciplines. Arguably, however, her greatest legacy is the enormous impact she has made as a research leader through her absolute commitment to scientific rigour and excellence, and her unquestionable integrity and commitment to fairness in society. She has contributed these attributes through her supervision and mentoring of students and early-career scientists, and her contributions to numerous bodies and panels, including the Royal Society and the Leverhulme Trust. Your career will have been directly or indirectly influenced by Pat, whether you know it or not. Pat has supervised over 40 PhD students, almost all of whom have carved successful scientific careers in roles that range from independent academics to senior conservation managers. Pat contributes to all the key programmes that now promote women in science. More critically, she has been an exceptional role model and mentor for young female scientists since the very beginning of her career, culminating in her becoming the first woman to be appointed to Glasgow's Regius Chair in Zoology. Directly and indirectly, she has undoubtedly contributed to the high numbers of women now working in ornithology within the UK. Pat's professional services have also involved extensive work within government and learned societies, where her achievements have been recognized through her appointment as President of both the International Society for Behavioural Ecology and the Association for the Study of Animal Behaviour. These activities have resulted in a number of awards, notably her election as a Fellow to the Royal Society of Edinburgh in 1997, and the Association for the Study of Animal Behaviour Scientific Medal in 2015. The strength and breadth of her work within ornithology now makes her an outstandingly deserving recipient of the BOU Goldman Salvin Prize.

The most common diet results in low reproduction in a generalist seabird.

Dietary specialization has been described across a wide range of taxa in the animal kingdom. Fitness consequences are, however, not well documented. We examined the reproductive consequences of different dietary specializations in the herring gull Larus argentatus, an omnivorous seabird, using an extensive dataset which includes breeding and dietary data of 10 successive years. We hypothesized that pairs that focused on prey of higher energetic value would yield higher fledging rates. An alternative hypothesis is that pairs that relied on more resources simultaneously would reproduce better. The novelty of this study is that we used continuous measurements representing dietary composition and degree of specialization rather than restricting our analysis to predefined categories. By relating these two continuous measurements for diet to several proxies for reproductive success, we show clear consequences of dietary choice. Most pairs concentrated on bivalves, a prey type not particularly rich in energy. Pairs feeding on energy‐rich prey (e.g., “domestic refuse and fishery discards”) during chick rearing were found to have a higher reproductive success, supporting the first hypothesis. Pairs that used more resources did not clearly have a higher reproductive success. The majority of the pairs did not switch to energy‐rich prey during chick rearing, despite low breeding outcome. We discuss how trade‐offs between factors such as resource availability, predictability, and the time and energy needed to obtain certain prey species may influence resource selection.

Common Eider and large gull and nesting associations in coastal Labrador

Apparent nesting associations between avian egg predators and their prey have received much interest, with gulls and waterfowl receiving considerable attention. We examined the co-occurrence of breeding large gulls (Herring Gull (Larus argentatus Pontoppidan, 1763) and Great Black-backed Gull (Larus marinus L., 1758)) and Common Eiders (Somateria mollissima L., 1758) along the coast of Labrador from 1998 to 2003. Nest counts for large gulls and eiders were undertaken by ground crews on 45–109 islands each year, counting 79–283 and 721–3424 nests annually, respectively. Gulls were more likely to nest on an island with nesting eiders (69.4%) than without nesting eiders (38.4%), and the probability and numbers of gulls nesting on an island increased as eider colony size increased. Large gulls were 1.76 times more likely to occupy islands that had nesting eiders in the previous year, while eiders were equally likely to colonize islands that did or did not have nesting gulls in the previous year. Eiders were no more likely to abandon islands that had nesting gulls in the previous year. In subarctic coastal landscapes, large gulls appear to preferentially nest in association with nesting eiders, while eiders appear not to avoid nesting islands based on the previous presence of large gulls.

Human Hair, Baltic Grey Seal (Halichoerus grypus) Fur and Herring Gull (Larus argentatus) Feathers as Accumulators of Bisphenol A and Alkylphenols

The purpose of the study was to determine the concentration of bisphenol A (BPA), 4-tert-octylphenol (OP), and 4-nonylphenol (NP), in human hair, the fur of Baltic grey seals and the feathers of herring gulls. Hair was collected from 42 volunteers, while grey seal fur (n = 17) came from the seal centre in Hel (Marine Station of Institute of Oceanography, University of Gdansk) and gull covert feathers (n = 26) were collected from dead herring gulls along the Southern Baltic coast. Assays of phenol derivatives were conducted using the high performance liquid chromatography with fluorescence detection technique. In human hair, the mean BPA concentration amounted to 411.2 ng g−1 dw, OP 131.2 ng g−1 dw, NP 4478.4 ng g−1 dw, in seal fur BPA 67.5 ng g−1 dw, OP 62.8 ng g−1 dw, NP 39.1 ng g−1 dw, and in feathers BPA 145.1 ng g−1 dw, OP 162.0 ng g−1 dw, NP 37.7 ng g−1 dw. The increase of the analysed EDCs in hair was significantly influenced by diet rich in products of marine origin, as well as hair colouring, heating up food in plastic containers, using home cleaning products without protective gloves and wearing newly purchased clothes without washing them first. The concentration of phenol derivatives in seal fur was influenced solely by the uniform diet rich in fish. In birds, the feeding area during molting significantly influenced the concentration of BPA, OP and NP found in covert feathers.

Microbiome and Antimicrobial Resistance Genes in Microbiota of Cloacal Samples from European Herring Gulls (Larus Argentatus).

IntroductionThe aim of the study was to determine microbiota in the cloacal samples of European herring gulls (Larus argentatus) and to compare a variety of genes encoding antimicrobial resistance in cultivable and non-cultivable bacteria.Material and MethodsCloacal samples from European herring gulls were collected from a Kaunas city dump. Cultivable microbiota were isolated, their microbial susceptibility was tested, and genes encoding antimicrobial resistance were detected. Additionally, a metagenomic study was performed using Next-Generation Sequencing (NGS).ResultsIn total, 697 different operational taxonomic units at genus level were detected; however, only 63 taxonomic units were detected at the amount of ≥0.1% of the total number of DNA copies. Catellicoccus marimammalium was found to have the highest prevalence. The bacterial amount of other genera was up to 5% with the most highly prevalent being Psychrobacter (4.7%), Helicobacter(4.5%), unclassified Enterococcaceae (3.2%), Pseudomonas (2.9%), and Brachyspira (2.6%).ConclusionsC. marimammalium are predominant microbiota in the cloacal samples of Larus argentatus. This species of gulls is a reservoir of bacteria carrying a wide-spectrum of genes encoding antimicrobial resistance. The same genes were detected in both cultivable microbiota and in the total DNA of the samples.