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Demographic rates such as recruitment and survival probability can vary considerably among populations of the same species due to variation in underlying environmental processes. If environmental processes are spatially correlated, nearby populations are expected to have more similar demographic rates than those further apart. Breeding populations and foraging ranges are spatially segregated in colonial seabirds, making them ideal for studying spatial patterns in demographic rates and their effects on local population dynamics. Here we explored variation in age-dependentsurvival probabilities across 14 colonies of Herring Gulls Larus argentatus breeding along the Dutch North Sea coast. We used long-term mark–recapture data of marked fledglings to estimate survival, and estimated spatial autocorrelation of survival probabilities. We assessed whether survival until recruitment age or until 10 years old (close to their expected lifespan) explained variation in population trajectories of each colony. Juvenile and adult survival showed a strong, but different, north-to-south gradient in survival probability, with lower juvenile but higher adult survival in northern colonies than southern colonies, whereas the spatial pattern of immature survival was less distinct. Neither recruitment nor the proportion of 10-year-old adults alive predicted whether a colony collapsed, declined, remained stable or increased. The distinct spatial pattern in survival suggests variation in regional food availability, which do not seem to drive local population dynamics. The absence of a link between survival and colony trajectories implies that connectivity between populations plays an important role affecting population dynamics.

Aim. The purpose of this research was to find out what local weather factors influence the nesting timing of the common gull (Larus canus). Material and Methods. The time of egg laying by the common gull was determined using data obtained during regular surveys over 8 years (1996‐1998, 2002‐2003, 2006‐2008) on the islands of Lake Bolshie Chany. Weather and climatic factors were assessed using open‐access databases. Results. It was been established that the start of egg‐laying in the colony of the common gull is determined by wind strength, the number of rainy days, the associated atmospheric pressure during the second decade of April, and the air temperature – the transition date at which the average daily air temperature rose above 0°C. In years with unstable spring temperatures, a relationship was revealed between the air temperature and the intensity of egg laying by the common gulls by day. In years when temperatures rise evenly, precipitation and wind speed become the main factors.Conclusion. We conclude that the egg‐laying dates of the common gull is influenced by weather variables during the whole nesting season and not predominantly by early season variables. We also show the importance of large‐scale climatic phenomena such as the EAWR in explaining variability in timing of the nesting of the common gull in Siberia. We suggest that future studies should focus on the effects of extremes in weather variables and global climatic phenomena.

The complete life cycle and the stages in the trematode Gynaecotyla adunca (Linton, 1905) (Yamaguti, 1939) from two different biotopes are described. The findings have revealed that, in the Black Sea, the trematodes G. adunca parasitize gastropods Hydrobia acuta (Draparnaud, 1805) as their first intermediate hosts and the shrimp Palaemon adspersus (Rathke, 1837) as the second intermediate hosts. According to our research, the definitive host is the gull Larus argentatus (Pontoppidan, 1763). Measurements, figures, and morphological characteristics of the species at all stages of development are provided.

An adult herring gull (Larus argentatus) found lethargic and moribund showed an open fracture of the right radius and ulna with necrosis of the surrounding tissue. Hematologic testing and plasma biochemical analysis revealed elevated creatinine kinase consistent with traumatic muscle damage in addition to hyperuricemia, hyperkalaemia, and hyperphosphatemia consistent with renal insufficiency. Increase in the acute phase protein Serum Amyloid A indicate a high degree of inflammation supported by leucocytosis, heterophilia, and hypoglycaemia pointing towards septicaemia. This case provides knowledge about Serum Amyloid A in gulls, and how bone fracture and secondary infection may affect gull blood haematology and biochemistry.

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.

The effects of growing urbanization have caused an increase in human-wildlife interactions in urban areas. Human-gull conflicts have been particularly studied during the breeding season when gulls cause an obvious nuisance in urban areas. However, with many gulls being present in urban areas throughout the year, stakeholders need knowledge of seasonal effects on local human-gull interaction dynamics. Here we present a comprehensive study on spatial and temporal variation of urban habitat use and human interactions with urban gulls, Larus spp., in Porto, Portugal. The work combined: (1) a large-scale study, using year-round monthly surveys to quantify gulls’ behaviour and their use of multiple urban habitats, with (2) a small-scale study, using 10-h daily urban surveys to capture gulls’ daily routines and interactions with humans during the winter and breeding seasons. We found a strong temporal effect in the number of gulls and human-gull interactions occurring in urban areas, with both highly increasing during winter. Habitats with higher urbanization intensity were mainly used by adult gulls, and the number of breeding-related conflicts reported by the human population peaked during the chick-rearing period. Still, during winter, several adult gulls kept occupying their rooftop nesting grounds, and the number of individuals foraging and interacting with humans in city-squares increased. This was mostly triggered by humans feeding birds. Therefore, when designing urban management landscape measures, seasonal variations of the urban gulls’ behaviour and habitat-use should be considered, as well as anthropogenic activities and human behaviour.

International audience; Wild animal species living in anthropogenic areas are commonly carriers of antimicrobial-resistant bacteria (AMRB), but their role in the epidemiology of these bacteria is unclear. Several studies on AMRB in wildlife have been cross-sectional in design and sampled individual animals at only one point in time. To further understand the role of wildlife in maintaining and potentially transmitting these bacteria to humans and livestock, longitudinal studies are needed in which samples are collected from individual animals over multiple time periods. In Europe, free-ranging yellow-legged gulls (Larus michahellis) commonly live in industrialized areas, forage in landfills, and have been found to carry AMRB in their feces. Using bacterial metagenomics and antimicrobial resistance characterization, we investigated the spatial and temporal patterns of AMRB in a nesting colony of yellow-legged gulls from an industrialized area in southern France. We collected 54 cloacal swabs from 31 yellow-legged gull chicks in 20 nests on three dates in 2016. We found that AMRB in chicks increased over time and was not spatially structured within the gull colony. This study highlights the complex occurrence of AMRB in a free-ranging wildlife species and contributes to our understanding of the public health risks and implications associated with ARMB-carrying gulls living in anthropogenic areas.

The current study explored the movement characteristics of 14 migratory bird species that wintered in the Republic of Korea between 2014 and 2020. The migratory bird movement information was obtained via a global positioning system operated by the Korean government. The velocity of movement, number of clusters, and size of clusters of the migratory bird species during their movement from their departing country to the Republic of Korea were estimated by applying a method based on density-based spatial clustering of applications with noise. The average movement velocity of pintails (Anas acuta) that departed from China or Russia was 32.77 km/h, the highest velocity among those measured for the 14 migratory bird species. The average number of clusters for cinereous vultures (Aegypius monachus) was 43.00, which was the largest cluster number observed. However, herring gulls (Larus argentatus) had the largest cluster area with an average cluster radius of 27.43 km while wintering in the Republic of Korea. The findings of the current study could be useful in increasing the effectiveness of the Korean national highly pathogenic avian influenza (HPAI) surveillance program. The human and material resources of the HPAI surveillance could be allocated after considering the results of this study, revealing the movement characteristics of wintering migratory birds in Korea. The HPAI surveillance program should include fecal or swab sampling to detect the HPAI virus in both pintail and bean goose (Anser faballis) wintering sites. Sampling of those sites should have a higher priority than that for other migratory bird wintering sites since pintail and bean goose move faster and form larger clusters.

With an increasing human population and expansion of urban settlements, wild animals are often exposed to humans. As humans may be a threat, a neutral presence or a source of food, animals will benefit from continuously assessing the potential risk they pose in order to respond appropriately. Herring gulls, Larus argentatus, are increasingly breeding and foraging in urban areas, and thus have many opportunities to interact with humans. We recently found that herring gulls take longer to approach food when being watched by a human. However, it is not known whether aversion to human gaze arises from experience with humans, and whether individual differences in responsiveness are a result of differential exposure. Here, we tested whether herring gulls' responses to human gaze differ according to their age class and urbanization of their habitat. We measured the gulls' flight initiation distance when an experimenter approached with either a direct or an averted gaze. Neither gull age class nor urbanization significantly influenced the effect of human gaze on flight initiation distance. However, as recently fledged juveniles responded strongly to the experimenter's gaze, aversion to human gaze may not require extensive exposure to humans to develop. Gulls in urban areas could be approached more closely than those in rural areas, consistent with findings in other species. These results indicate that gaze aversion is present early in development and that exposure to humans may influence gulls' responses to perceived risk from humans. Investigating the processes generating individual differences in responses to humans will provide further insights into human–wildlife interactions and the effects of urbanization.

Kleptoparasitism is a foraging strategy where one individual steals a procured food item from another individual. Individual kleptoparasites can optimize their foraging strategy by targeting more profitable hosts or by modifying their behaviour to expend less energy than they would by foraging independently. Herring gulls, Larus argentatus, kleptoparasitize Atlantic puffins, Fratercula arctica, by intercepting adults as they return to their burrows with fish for their chicks. While this system has been studied extensively, much remains unknown, particularly from the herring gull's perspective. We tested predictors of herring gull host choice and the probability of success during kleptoparasitic attacks by conducting 73 30-minute focal samples of individual herring gulls at a breeding colony in Newfoundland, Canada. We recorded each puffin that approached the focal gull, categorizing them according to prey type carried, whether or not they landed, and whether or not they were attacked. For those puffins that were attacked, we also noted whether the gull succeeded in obtaining prey. Herring gulls did not attack puffins at random, but, rather, preferentially attacked puffins that carried larger prey, had already completed their landing, and landed closer to and/or in front of the gull. Gulls tended to be more successful at stealing a puffin's food when they attacked landed puffins and made physical contact with the puffin, but not when the puffin landed closer to them or when they were oriented towards the puffin. These findings suggest that herring gulls optimize their kleptoparasitic foraging strategy by targeting more profitable hosts.

Environmental factors that can influence telomeres are diverse, but the association between telomeres and exposure to environmental contaminants is yet to be elucidated. To date, prior studies have focused on legacy persistent chlorinated pollutants (POPs), while the effects of poly- and perfluoroalkyl substances (PFAS) have been poorly documented. Here, we investigated the associations among PFAS congeners, absolute telomere length (cross-sectional approach), and telomere dynamics (rate of telomere length change over time, longitudinal approach) in one of the most contaminated arctic top predators, the glaucous gull Larus hyperboreus from Svalbard. We further estimated the effect of PFAS on apparent survival rates and re-sighting probabilities using a 10-year capture/recapture dataset (2010–2019). We found that birds exposed to higher concentrations of perfluorononadecanoate (PFNA) (median of 1565 pg/mL of ww in males and 1370 pg/mL of ww in females) and perfluorotetradecanoate (PFTeDA) (median of 370 pg/mL of ww in males and 210 pg/mL of ww in females) showed the slowest rate of telomere shortening. We also found that high blood concentrations of perfluorooctanoate (PFOA) (median of 120 pg/mL of ww in males and 150 pg/mL of ww in females) and perfluorohexanesulfonate (PFHxS) (median of 495 pg/mL of ww in males and 395 pg/mL of ww in females) were positively associated with higher re-sighting probabilities and apparent survival in males but not in females. Our work is the first to report an association between single PFAS compounds and telomeres, and the first to link PFAS exposure with survival probabilities, suggesting that the effect of PFAS exposure might be more tied to the type of compound rather than the total concentration of PFAS.

This article presents an elaboration of the protocol for the method of sexing wild birds based on the polymorphism of the CHD gene using P2/P8 primer for Common Pheasant – Phasianus colchicus (Linnaeus, 1758; Galliformes, Phasianidae); Silver Lofur or Silver Pheasant – Lophura nycthemera (Linnaeus, 1758; Galliformes, Phasianidae), Budgerigar – Melopsittacus undulatus (Shaw, 1805; Psittaciformes, Psittacidae), Herring Gull – Larus argentatus (Pontoppidan, 1763; Charadriiformes, Laridae), and White Stork – Ciconia ciconia (Linnaeus, 1758; Ciconiiformes, Ciconiidae). Blood samples were taken from Common Pheasant, Silver Pheasant and White Stork using the “drop of blood on paper” method. For the Budgerigar and the Herring Gull, DNA was isolated from the feather follicle. To isolate DNA, a commercial NeoPrep 100 DNA reagent kit (Neogen, Ukraine) was used. Primers P2/P8 were used for PCR; PCR was performed using GenPac PCR Core reagents (Neogen, Ukraine). We selected the optimal amount of Tag polymerase, the amount of DNA and primers and, according to the amount of reagents, set acceptable amplification modes and electrophoresis agarose gel percentage. Prior to PCR, additional DNA gel electrophoresis purification is proposed, which increases the percentage of positive sex determination results. It was found that the ideal mixture for the 5 bird species was an amplification mixture (total volume 20 µL, containing 1 U Tag polymerase, 100 ng DNA and 0.6 µM of each primer). The amplified CHD-Z fragment of Common and Silver pheasants is of ~340 n. p., CHD-W ~360 n. p. Herring Gull and Budgerigar have ~350 n. p. of CHD-Z length, and ~400 n. p. of CHD-W length, White Stork has its CHD-Z of ~ 370 n. p. long. It is advisable to investigate the genome of the experimental bird species using horizontal electrophoresis in agar’s gel with the concentration of 5%, which makes it possible to clearly visualize the female genotype. The universal protocol of the method of sex determination based on polymorphism of the CHD gene for the 5 studied bird species is described. These results of the study led to the conclusion that for the simultaneous sexing of several species of birds, it is advisable to develop a unified protocol for determining the status of the CHD gene, with the aim of clarifying the gender, as well as new approaches in ornithology and ecology aimed at determining interspecific differences associated with gene polymorphism. Identification of differences in fragment sizes may be useful for identifying the species in cases when birds form mixed pairings for taxonomic and phylogenetic comparisons.

Egg quality (size, energy density) is important in determining early survival of birds. Here, we examine temporal (1981–2019) trends in herring gull (Larus argentatus) egg volume and energy density at breeding colonies on all five Laurentian Great Lakes. Temporal declines in egg volume were observed at 4/6 colonies on the upper Great Lakes (Lakes Superior, Michigan, Huron). On the lower Great Lakes (Lakes Erie, Ontario, and connecting channels) egg volume declined at 3/8 colonies and increased at one site. Egg energy density (kJ/g of egg contents) declined at 4/6 upper Great Lakes colonies and at 2/8 lower Great Lakes colonies. All of the upper Great Lakes colonies showed declines in either egg volume or energy density, or both, and these declines were related to dietary markers in eggs (fatty acids, stable nitrogen and carbon isotopes). On the lower Great Lakes and connecting channels, declines in egg volume or energy density were related to dietary endpoints in 3/5 instances. An information-theoretic approach indicated that trends in egg volume were best explained at the colony level while egg energy density trends were best explained by lake of origin. Diet-related declines in herring gull egg quality are likely a reflection of broad-scale ecosystem changes limiting aquatic food availability for gulls, particularly on the upper Great Lakes. These changes may be contributing to population declines in herring gulls and other surface-feeding aquatic birds. This study highlights the value of long-term monitoring of wildlife for identifying ecosystem change.

The reproductive cost hypothesis predicts that parents with low investment capacity (e.g., those in poor condition) should produce the larger sex (usually males) less often so as to minimize the risk of current reproductive failure and/or a decrease in their residual reproductive value. The study aimed to test whether offspring sex ratio bias in replacement clutches of the Mew Gull (MG;Larus canus) and Black-headed Gull (BHG;Chroicocephalus ridibundus) exposed to different food conditions was in agreement with predictions of the reproductive cost hypothesis. Food availability was experimentally modified before egg laying. Our experimental treatment affected hatching sex ratio, being also significant the effect of laying order and species identity. For both gull species, parents that were provided with supplemental food had more sons at hatching than unfed (control) pairs. This was particularly so if they were fed until production of a replacement clutch. This gradient in hatching sex ratio was much more pronounced in MG than in BHG. In both gull species, sons hatched more often from first laid (A) than from second (B) or third-laid egg (C). Five days after hatching, the sex ratio of surviving chicks was dependent mainly on the experimental treatment and egg sequence. Unlike the time of hatching, there was no important effect of species × treatment interaction. In both gull species, the brood sex-ratio was clearly male-biased in parents receiving supplemental feeding. However, differences between experimental groups were less extreme than at hatching. Chicks hatched from C-egg had much lower survival than chicks from the first two eggs (A- and B-egg), irrespective of sex, treatment, or species. Supplementary feeding was associated with improved chick survival for both gull species, although this effect was dependent on chick gender. Surprisingly, in the case of control broods (i.e., broods whose parents did not receive supplementary food), male chicks survived better than female chicks, but the opposite was true for broods in which parents were fed. There was an overall tendency for higher survival of BHG chicks than MG chicks. During the early-chick period, competition between siblings and the related differentiated mortality of chicks from A-, B-, and C-eggs, constituted a mechanism which shaped the brood sex ratio bias. In this context, differences in the sex ratio bias in eggs of different rank (A, B, C) at hatching were important. The results appear to fulfil the expectations of the reproductive cost hypothesis. For the species with greater sexual dimorphism (MG), a relationship between the condition of parents and the expected bias of sex ratio was visible only at hatching, which may indicate that this feature is not significant in shaping the sex ratio bias in MG.

Trematode specimens were collected from the intestine of a herring gull, Larus argentatus, which was found in a critical condition on the shore of a small island (Yubu-do, Seocheon-gun, Chungcheongnam-do) located at the western coast of the Korean peninsula. Total 11 specimens of intestinal flukes, including 3 Cryptocotyle lingua (Heterophyidae), 1 Himasthla alincia (Echinostomatidae), 5 Cardiocephaloides medioconiger (Strigeidae), and 2 Diplostomum spathaceum (Diplostomidae), were recovered. C. lingua was morphologically characterized by the presence of a large ventrogenital apparatus and 2 obliquely tandem testes. H. alincia had an elongated body and a head collar equipped with 31 collar spines. C. medioconiger had a bisegmented body and a voluminous copulatory bursa containing the seminal vesicle and ejaculatory duct. D. spathaceum also had a bisegmented body and its vitellaria extended up to the anterior border of the tribocytic organ. It is of note that C. lingua is potentially zoonotic that can occur in birds and humans. Three of them, i.e., C. lingua, C. medioconiger, and D. spathaceum, are new trematode fauna in Korea. Studies on trematode fauna of migratory birds should be continued in Korea.

Larus ridibundus Linnaeus, 1766 LITERATURE. — Thonnérieux et al. (1989, 1990); Dowsett (1993); Weesie (1996); Borrow & Demey (2001, 2014); Sinclair & Ryan (2010); Dowsett et al. (2013). STATUS. — Palaearctic migrant., Published as part of Boano, Giovanni, Belemsobgo, Urbain, Silvano, Fabrizio, Hema, Emmanuel M., Belemsobgo, Aristide, Dimobe, Kangbéni & Pavia, Marco, 2022, An annotated checklist of the birds of Burkina Faso, pp. 27-107 in Zoosystema 44 (2) on page 53, DOI: 10.5252/zoosystema2022v44a2, http://zenodo.org/record/5999691, {"references":["THONNERIEUX Y., WALSH J. F. & BORTOLI L. 1989. - L'avifaune de la ville de Ouagadougou et ses environs (Burkina Faso). Malimbus 11: 7 - 39.","THONNERIEUX Y., WALSH J. F. & BORTOLI L. 1990. - Errata to l'avifaune de la ville de Ouagadougou et ses environs (Burkina Faso). Malimbus 12: 58 - 59.","DOWSETT R. J. 1993. - Afrotropical avifaunas: annotated country checklists, in DOWSETT R. J. & DOWSETT- LEMAIRE F. (eds). A Contribution to the Distribution and Taxonomy of Afrotropical and Malagasy birds Tauraco Research Report 5, Tauraco Press, Liege: 1 - 322.","WEESIE P. D. M. 1996. - Les oiseaux du Sahel Burkinabe: peuplements d'hiver, capacite de charge des sites. Alauda 64: 307 - 332.","BORROW N. & DEMEY R. 2001. - Birds of Western Africa. Christopher Helm, London, 832 p.","BORROW N. & DEMEY R. 2014. - Field Guide of the Birds of Western Africa. II edition. Christopher Helm, London, 592 p.","SINCLAIR I. & RYAN P. 2010. - Birds of Africa south of the Sahara. II edition. Struik Nature, Cape Town, 768 p.","DOWSETT R. J., ATKINSON P. W. & CADDICK J. A. 2013. - Checklist of the birds of Burkina Faso: 1 - 12. https: // www. africanbirdclub. org / [accessed 14 October 2013]."]}

Larus cirrocephalus poiocephalus Swainson, 1837 LITERATURE. — Dowsett (1993); Balanca & de Visscher (1997); Borrow & Demey (2001, 2014); Balanca et al. (2007); Sinclair & Ryan (2010); Dowsett et al. (2013). STATUS. — Afrotropical migrant., Published as part of Boano, Giovanni, Belemsobgo, Urbain, Silvano, Fabrizio, Hema, Emmanuel M., Belemsobgo, Aristide, Dimobe, Kangbéni & Pavia, Marco, 2022, An annotated checklist of the birds of Burkina Faso, pp. 27-107 in Zoosystema 44 (2) on page 53, DOI: 10.5252/zoosystema2022v44a2, http://zenodo.org/record/5999691, {"references":["DOWSETT R. J. 1993. - Afrotropical avifaunas: annotated country checklists, in DOWSETT R. J. & DOWSETT- LEMAIRE F. (eds). A Contribution to the Distribution and Taxonomy of Afrotropical and Malagasy birds Tauraco Research Report 5, Tauraco Press, Liege: 1 - 322.","BALANCA G. & DE VISSCHER M. - N. 1997. - Composition et evolution saisonniere d'un peuplement d'oiseaux au nord du Burkina Faso (Nord-Yatenga). Malimbus 19: 68 - 94.","BORROW N. & DEMEY R. 2001. - Birds of Western Africa. Christopher Helm, London, 832 p.","BORROW N. & DEMEY R. 2014. - Field Guide of the Birds of Western Africa. II edition. Christopher Helm, London, 592 p.","BALANCA G., CORNELIS D. & WILSON R. 2007. - Les oiseaux du complexe WAP. ECOPAS. Cirad, Montpellier.","SINCLAIR I. & RYAN P. 2010. - Birds of Africa south of the Sahara. II edition. Struik Nature, Cape Town, 768 p.","DOWSETT R. J., ATKINSON P. W. & CADDICK J. A. 2013. - Checklist of the birds of Burkina Faso: 1 - 12. https: // www. africanbirdclub. org / [accessed 14 October 2013]."]}

Larus modestus Tschudi, 1843 Grey gull���Gaviota garuma Quadraceps punctatus lingulatus (Waterston, 1914), Published as part of Gonza �� Lez-Acun, Daniel A. & Palma, Ricardo L., 2021, An annotated catalogue of bird lice (Insecta: Phthiraptera) from Chile, pp. 1-151 in Zootaxa 5077 (1) on page 124, DOI: 10.11646/zootaxa.5077.1.1, http://zenodo.org/record/5766642, {"references":["Waterston, J. (1914) On some ectoparasites in the South African Museum, Cape Town. Annals of the South African Museum, 10 (9), 271 - 324, 2 pls. https: // doi. org / 10.5962 / bhl. part. 9318"]}

Individual diet specialization is known to occur in populations of generalist predators, where specific individuals develop specialist feeding strategies. Diet specialization has been reported in many raptor species, and it may be an important driver of intraspecific population structure. Here, we quantify the diet of five breeding pairs of Peregrine Falcons Falco peregrinus from an offshore island determined from prey remains collected over four breeding seasons. Three prey species accounted for 69.8 % of total prey frequency, with Manx Shearwater Puffinus puffinus the primary prey accounting for 47.3 % by frequency and 40.8 % by biomass. Herring Gull Larus argentatus was the second most important prey species by frequency (13.8 %) and biomass (29.8 %) followed by Domestic Pigeon Columba livia (frequency = 8.7 %, biomass = 7.0 %). Predation frequency on specific prey groups varied substantially between breeding pairs and months. Two pairs specialized on Manx Shearwater, one pair specialized on Herring Gull and Manx Shearwater, with the remaining two pairs having a relatively generalist diet of Manx Shearwaters, Domestic Pigeon and small passerines. Predation on Manx Shearwaters increased throughout the breeding season with a peak in total diet frequency of 63.8 % in July, with a concurrent decrease in Herring Gull predation frequency. Higher percentage of Manx Shearwater in the diet was able to explain 87 % of the variation in a narrower dietary breadth for the Peregrine pairs. Our results suggest individual diet specialization may be important for understanding population density in insular raptor populations.

We present the first records of fungi associated with feathers from seabirds and sea ducks in the Canadian Arctic and sub-Arctic. Birds sampled in Nunavut and Newfoundland (Canada) included the Common Eider (Somateria mollissima), King Eider (S. spectabilis), Black-legged Kittiwake (Rissa tridactyla), Northern Fulmar (Fulmarus glacialis), Glaucous Gull (Larus hyperboreus), Black Guillemot (Cepphus grylle), and Thick-billed Murre (Uria lomvia). In total 19 fungal species were cultured from feathers, identified using ITS rDNA barcoding, and screened for their ability to degrade keratin using a keratin azure assay. Our results indicate that 1) of the 19 isolates, 74% were ascomycetes, while the remaining 26% were basidiomycetes (yeasts); 2) 21% of the ascomycete isolates demonstrated keratinolytic activity (a known pathogenicity factor for fungi that may potentially be harmful to birds); 3) the largest number of fungi were cultured from the sampled Thick-billed Murre; and 4) based on a multiple correspondence analysis, there is some indication that both the King Eider and the Thick-billed Murre collected in the low Arctic had distinct fungal communities that were different from each other and from the other birds sampled. Although our sample sizes were small, initial trends in point (4) do demonstrate that additional study is merited to assess whether the fungal community differences are influenced by variation in the known ecologies of the avian hosts and fungi identified.

Among seabirds, lesser black-backed gulls (Larus fuscus) are considered to be at high risk of colliding with offshore wind turbines. In this respect, we used GPS tracking data of lesser black-backed gulls caught and tagged in two colonies along the Belgian North Sea coast (Ostend and Zeebrugge) to study spatial patterns in the species’ presence and behaviour in and around the Thornton Bank offshore wind farm (OWF). We found a significant decrease in the number of GPS fixes of flying birds from up to a distance of at least 2000 m towards the middle of the wind farm. Non-flying birds showed a similar avoidance of the wind farm interior, yet presence strongly peaked right at the wind farm’s edge, demonstrated to represent gulls perching on the outer turbine jacket foundations. The findings of this study reveal a strong within-wind farm variability in bird density, a most crucial parameter in collision risk modelling. The method presented here is straightforward and similar studies conducted at other wind farm sites on a range of large gull species (Larus sp.) would allow to assess the potential and species-specific variation in meso-scale response patterns and to gain insight in the underlying ecological incentives, which in turn would provide widely applicable and much-needed input for (cumulative) collision impact assessments.

In Lake Superior's Pukaskwa National Park (PNP) in northern Ontario, Canada, herring gull (Larus argentatus) population size is used as an indicator of ecological integrity. Since the 1970s, gull populations have declined by 70% suggesting deteriorating park conditions. However, most other rated park indicators show stable or positive trends. Here, we focus on reconciling these seemingly disparate trends through a better understanding of factors regulating PNP gull populations. Lake-wide declines in surface-schooling prey fish may be limiting aquatic food resources for PNP gulls. To investigate this, we examined gull population trends in different parts of the park in the context of food availability. Gull diets were assessed using regurgitated pellets, egg stable isotopes (nitrogen, carbon) and fatty acids. Population declines were more severe in southern PNP compared to northern PNP and inter-region differences in bird diets likely contributed to these population trends. Gulls in the south relied to a greater extent on dwindling aquatic food resources, i.e., prey fish, while birds in northern PNP supplemented their diets with anthropogenic foods, i.e., garbage. Recognizing that regional declines in aquatic food availability have occurred across eastern Lake Superior is important for the interpretation of PNP gull population trends. Wide-scale ecological changes affecting PNP suggest that factors limiting PNP's herring gull population are not park-specific but, instead, reflect broader ecosystem-wide changes. Defining an appropriate threshold based on current knowledge of ecological conditions on Lake Superior is critical for using herring gull populations as an indicator of park ecological integrity.

Golden Eagles Aquila chrysaetos colonized the northern California Channel Islands, an archipelago located off the coast of southern California, USA, in the early 1990s, owing in part to the presence of Feral Pigs Sus scrofa. Eagles preyed on piglets and on the endemic Island Fox Urocyon littoralis, driving three endemic subspecies of the Island Fox (U. l. santacruzae, U. l. santarosae and U. l. littoralis) toward extirpation. Using stable isotopes (δ¹³C and δ¹⁵N) measured from feathers and blood of Golden Eagles and from meat and bone of their prey, along with the proportion of prey consumed estimated from nest excavations as informative priors, we show that shifts in Eagle isotopic signatures tracked community reorganization: when pigs and foxes were abundant, Eagles consumed them in higher proportions than other prey; when foxes became scarce owing to Eagle predation, Eagle diet shifted toward pigs, but also diversified to include Common Ravens Corvus corax and seabirds (Larus spp. and Phalacrocorax spp.); and finally, after pigs were eradicated and 35 Golden Eagles had been captured and removed from Santa Cruz Island, a lone remaining pair of Eagles reversed their diet to include more foxes. Our findings reveal that shifts in stable isotope signatures from tissues of an apex predator can be used as a general proxy to monitor changes in the prey community; however, if sample sizes are small, informative priors are both essential and overwhelmingly influential, and changes in abundance of preferred prey may mask or fail to reveal changes in less preferred prey. Given that apex predators are at the top of trophic hierarchies, that they are often important drivers of community structure and that they sample prey continuously from their community, isotopic signatures of their tissues may be useful for monitoring community change.

Mercury enters the body of seabirds in its most toxic organic form, i.e. methylmercury, mainly via the alimentary tract. Inside the body, mercury is transformed into less toxic forms and accumulates in the internal organs. The process of mercury removal from the body, most effective during the formation of new feathers and claws, is beneficial for the bird. The presented research was undertaken on account of the high affinity of mercury to keratin – a protein that forms feathers and claws – to compare the concentration levels (HgTOT) in these structures and to assess their contribution to the purification of the body of herring gulls (Larus argentatus) Bird feathers are the only epidermal structure that is extensively described in the literature, whereas the claws have so far been poorly researched. The study has shown that mercury in claws is built in as effectively as in feathers, and the obtained concentrations were within a wide range of 127.2–5341.5 ng HgTOT g–1 of dry weight. In addition, the concentrations of total mercury accumulated in the claws were a better reflection of Hg levels in internal organs compared to feathers.

Sea‐ice coverage is a key abiotic driver of annual environmental conditions in Arctic marine ecosystems and could be a major factor affecting seabird trophic dynamics. Using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in eggs of thick‐billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis), glaucous gulls (Larus hyperboreus), and black‐legged kittiwakes (Rissa tridactyla), we investigated the trophic ecology of prebreeding seabirds nesting at Prince Leopold Island, Nunavut, and its relationship with sea‐ice conditions. The seabird community of Prince Leopold Island had a broader isotopic niche during lower sea‐ice conditions, thus having a more divergent diet, while the opposite was observed during years with more extensive sea‐ice conditions. Species' trophic position was influenced by sea ice; in years of lower sea‐ice concentration, gulls and kittiwakes foraged at higher trophic levels while the opposite was observed for murres and fulmars. For murres and fulmars over a longer time series, there was no evidence of the effect of sea‐ice concentration on species' isotopic niche. Results suggest a high degree of adaptation in populations of high Arctic species that cope with harsh and unpredictable conditions. Such different responses of the community isotopic niche also show that the effect of variable sea‐ice conditions, despite being subtle at the species level, might have larger implications when considering the trophic ecology of the larger seabird community. Species‐specific responses in foraging patterns, in particular trophic position in relation to sea ice, are critical to understanding effects of ecosystem change predicted for a changing climate.

Gulls (Larus spp.) have frequently been reported to carry Escherichia coli exhibiting antimicrobial resistance (AMR E. coli); however, the pathways governing the acquisition and dispersal of such bacteria are not well described. We equipped 17 landfill-foraging gulls with satellite transmitters and collected gull faecal samples longitudinally from four locations on the Kenai Peninsula, Alaska to assess: (a) gull attendance and transitions between sites, (b) spatiotemporal prevalence of faecally shed AMR E. coli, and (c) genomic relatedness of AMR E. coli isolates among sites. We also sampled Pacific salmon (Oncorhynchus spp.) harvested as part of personal-use dipnet fisheries at two sites to assess potential contamination with AMR E. coli. Among our study sites, marked gulls most commonly occupied the lower Kenai River (61% of site locations) followed by the Soldotna landfill (11%), lower Kasilof River (5%) and upper Kenai River (1%). Gulls primarily moved between the Soldotna landfill and the lower Kenai River (94% of transitions among sites), which were also the two locations with the highest prevalence of AMR E. coli. There was relatively high spatial and temporal variability in AMR E. coli prevalence in gull faeces and there was no evidence of contamination on salmon harvested in personal-use fisheries. We identified E. coli sequence types and AMR genes of clinical importance, with some isolates possessing genes associated with resistance to as many as eight antibiotic classes. Our findings suggest that gulls acquire AMR E. coli at habitats with anthropogenic inputs and subsequent movements may represent pathways through which AMR is dispersed.

Per- and polyfluoroalkyl substances (PFAS) are a diverse group of fluorinated organic chemicals that have been used in industrial and consumer applications since the 1950s. PFAS are resistant to chemical and biological degradation and are ubiquitous in the environment, including in water, sediment, and biota in the Laurentian Great Lakes. This critical review evaluates the spatial and temporal variability of commonly studied perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) in the Great Lakes by synthesizing data collected in water, surface sediment, sediment cores, lake trout (Salvelinus namaycush), and herring gull (Larus argentatus) eggs. The lowest PFAS concentrations in all matrices are detected in Lake Superior, which is located in the most pristine region of the Great Lakes Basin. In contrast, higher concentrations are observed in Lakes Erie and Ontario, which are more impacted by industrial activity and wastewater discharge. The distribution of individual PFAS compounds also varies across the lakes in response to changes in PFAS sources, with higher proportions of PFSAs in the eastern lakes. Sediment and biota are enriched in long chain PFSAs and PFCAs relative to concentrations in the water column, as expected based on predicted partitioning behavior. Sediment cores and bioarchives consistently demonstrate that PFAS concentrations increased in the Great Lakes from the initial time points until the early 2000s. The available data indicate that PFOS and PFOA concentrations decline after this period in the upper Great Lakes, but are stable in Lake Ontario. However, these trends depend on the lake, the individual compound, and the organism considered.

Monitoring of ornithofauna in wintering areas of waterbirds is an important component of the vulnerable bird species conservation and species diversity as a whole. The environmental conditions are favorable for wintering of waterbirds in the lower tail of the Dnieper River hydroelectric power station (HES) that determines the mass concentration of birds in this area. The species composition and abundance of waterbirds were studied at the Dnieper River HES (47.856N, 35.073E) during winters of 2015-2019. In total 77,741 individuals of waterbirds of 26 species, 8 families and 7 orders were counted. Bird counts were conducted in December and January. The water area and coast of the Dnieper River were inspected visually from the dam of HES to the bridge across the Dnieper River in the city of Zaporizhzhia. During the research period, 12 to 18 waterbirds species were found in the wintering bird communities. The number of birds in communities ranged from 5318 to 17072 individuals. Mergus merganser was an absolute dominant of winter communities in January of 2016 and 2017, years with prolonged frosts and persistent ice formation. The index of concentration of dominance was the highest in those years (0,49). In winters of 2017/2018–2018/2019 the temperature regime was milder, and the dominant species was Larus canus. The subdominant species was Larus cachinnans. The index of concentration of domination was then the lowest, 0,22. The ratio of birds of protected species in wintering bird communities did not exceed 0.5 % in the Dnieper River HES area in winters of 2015/2016–2018/2019. Winter communities of 2008-2009 were most similar to those observed in 2016-2017 (CS = 0,74). By the ratios of each species the winter communities of 2008/2009 years were the most similar to the communities of 2015/16 (CN = 0,73).

Five peat sequences were studied to identify the time the little auk Alle alle colonies originated in the Hornsund area (Spitsbergen). Elemental and stable isotope analysis of nitrogen and carbon was applied as markers for bird activity. The peat sequences were dated with 210Pb and radiocarbon methods. The results showed that peat development related to seabird activity is significantly older (at least 300 years old) in localities closer to the fjord's mouth (west) than those located deeper in the fjord (east), which are ~100 years old. Isotopic signals indicated that bird activity in the western localities decreased simultaneously with the growth of the eastern colonies. Colonization by birds of new localities correlated with the termination of the Little Ice Age and the meaningful decrease in the glacier area of the region. Hence, we suggest that the availability of new localities for nesting in talus cones, nival moraines and lateral moraines on gentle mountain slopes with south-eastern exposition attracted the little auk due to better thermal conditions, isolation from strong westerly winds and better protection from predation by gull Larus hyperboreus. The expansion of little auks to the new localities was fast (20–30 yrs), and there are no records of changes in bird impacts on the tundra environment after 1920.

Opportunist gulls use anthropogenic food subsidies, which can bolster populations, but negatively influence sensitive local ecosystems and areas of human settlement. In the eastern Gulf of Maine, Canada, breeding herring gulls Larus argentatus have access to resources from aquaculture, fisheries and mink farms, but the relative influence of industry on local gull populations is unknown. Our objectives were to 1) assess use of natural and anthropogenic habitats by herring gulls from multiple colonies, 2) evaluate variation among colonies in use of distinct resource types within these habitats and 3) highlight areas of high gull:industry interaction. Using GPS devices on 39 gulls from four colonies, we identified visitation behaviour (slow, localized movements) and assigned visits to nine resource types. To evaluate the spatial distribution of visits, we created a use intensity index, reflecting both fidelity (i.e. repeated visits) and time spent in specific areas. All four anthropogenic resource types were heavily used (56 ± 11% of visiting time across colonies), notably, fish plants and mink farms. Despite large distances among three colonies, birds overlapped at particular distant, inland mink farms. In contrast, birds from close colonies overlapped in visitation to specific nearby resources (e.g. fish plants and human settlement), and otherwise diverged in distribution and use of offshore and coastal areas. Birds from three colonies also made frequent, long visits to uninhabited islands. Industry is clearly influencing the behaviour of breeding gulls in the eastern Gulf of Maine, Canada, where birds are travelling great distances or spending large proportions of time interacting with anthropogenic resources, while otherwise paying lengthy visits to nearby coastal islands. Studies have shown that concentrations of gulls can have harmful direct and indirect ecological and societal impacts. Our findings have implications for the management and regulation of industry to mitigate detrimental effects on local ecosystems and humans.

Avian keratin disorder (AKD), a disease characterized by debilitating beak overgrowth but with unknown etiology, has increasingly affected wild bird populations since the 1990s. We previously showed that a novel picornavirus, Poecivirus, is closely correlated with disease status in Black-capped Chickadees (Poecile atricapillus) in Alaska. However, our knowledge of the relationship between Poecivirus and beak deformities in other species and other geographic areas remains limited. The growing geographic scope and number of species affected by AKD-like beak deformities require a better understanding of the causative agent to evaluate the population-level impacts of this epizootic. Here, we tested eight individuals from six avian species with AKD-consistent deformities for the presence of Poecivirus: Mew Gull (Larus canus), Hairy Woodpecker (Picoides villosus), Black-billed Magpie (Pica hudsonia), Northwestern Crow (Corvus caurinus), Red-breasted Nuthatch (Sitta canadensis), and Blackpoll Warbler (Setophaga striata); individuals were sampled in Alaska and Maine (1999-2016). We used targeted PCR followed by Sanger sequencing to test for the presence of Poecivirus in each specimen, and to obtain viral genome sequence from virus-positive host individuals. We detected Poecivirus in all individuals tested, but not in negative controls. Furthermore, we used unbiased metagenomic sequencing to test for the presence of other pathogens in six of these specimens (Hairy Woodpecker, two Northwestern Crows, two Red-breasted Nuthatches, Blackpoll Warbler). This analysis yielded additional viral sequence from several specimens, including the complete coding region of Poecivirus from one Red-breasted Nuthatch, which we confirmed via targeted PCR followed by Sanger sequencing. This study demonstrates that Poecivirus is present in individuals with AKD-consistent deformities from six avian species other than Black-capped Chickadee. While further investigation will be required to explore whether there exists a causal link between this virus and AKD, this study demonstrates that Poecivirus is not geographically restricted to Alaska, but rather occurs elsewhere in North America.

Birds’ behavioral response to brood parasitism can be influenced not only by evolution but also by context and individual experience. This could include nest sanitation, in which birds remove debris from their nests. Ultimately, nest sanitation behavior might be an evolutionary precursor to the rejection of parasitic eggs. Proximately, the context or experience of performing nest sanitation behavior might increase the detection or prime the removal of parasitic eggs, but evidence to date is limited. We tested incubation-stage nests of herring gulls Larus argentatus to ask whether nest sanitation increased parasitic egg rejection. In an initial set of 160 single-object experiments, small, red, blocky objects were usually rejected (18 of 20 nests), whereas life-sized, 3D-printed herring gull eggs were not rejected whether red (0 of 20) or the olive-tan base color of herring gull eggs (0 of 20). Next, we simultaneously presented a red, 3D-printed gull egg and a small, red block. These nests exhibited frequent nest sanitation (small, red block removed at 40 of 48 nests), but egg rejection remained uncommon (5 of those 40) and not significantly different from control nests (5 of 49) which received the parasitic egg but not the priming object. Thus, performance of nest sanitation did not shape individuals’ responses to parasitism. Interestingly, parents were more likely to reject the parasitic egg when they were present as we approached the nest to add the experimental objects. Depending on the underlying mechanism, this could also be a case of experience creating variation in responses to parasitism.

Wild birds may host and spread pathogens, integrating the epidemiology of infectious diseases. Particularly, Larus spp. have been described as responsible for the spread of many enteric diseases, primarily because of their large populations at landfill sites. The aim of this study was to examine the role of yellow-legged gulls as a source of enteropathogenic bacteria such as Campylobacter spp., Salmonella spp., Shiga toxin-producing Escherichia coli and Yersinia spp., with particular attention to antibiotic-resistant strains. Enteropathogenic bacteria were isolated from 93/225 yellow-legged gulls examined from April to July, during a four-year period (2016–2019). Specifically, Campylobacter spp. was isolated from 60/225 samples (26.7%), and identified as C. coli (36/60) and as C. jejuni (24/60). Salmonella spp. was isolated from 3/225 samples (1.3%), and identified as Salmonella arizonae. Shiga toxin-producing E. coli were isolated from 30/225 samples (13.3%) samples, and serotyped as E. coli O128 (12/30) O26 (9/30), O157 (6/30) and O11 (3/30), Yersinia spp. was never detected. Isolated strains exhibited multidrug resistance, including vitally important antibiotics for human medicine (i.e., fluoroquinolones, tetracyclines). Our study emphasizes the importance of yellow-legged gulls as potential reservoirs of pathogenic and resistant strains and their involvement in the dissemination of these bacteria across different environments, with resulting public health concerns.

Parental age can affect offspring telomere length through heritable and epigenetic-like effects, but at what stage during development these effects are established is not well known. To address this, we conducted a cross-fostering experiment in common gulls (Larus canus) that enabled us distinguish between pre- and post-natal parental age effects on offspring telomere length. Whole clutches were exchanged after clutch completion within and between parental age classes (young and old) and blood samples were collected from chicks at hatching and during the fastest growth phase (11 days later) to measure telomeres. Neither the ages of the natal nor the foster parents predicted the telomere length or the change in telomere lengths of their chicks. Telomere length (TL) was repeatable within chicks, but increased across development (repeatability = 0.55, intraclass correlation coefficient within sampling events 0.934). Telomere length and the change in telomere length were not predicted by post-natal growth rate. Taken together, these findings suggest that in common gulls, telomere length during early life is not influenced by parental age or growth rate, which may indicate that protective mechanisms buffer telomeres from external conditions during development in this relatively long-lived species.

Urban herring gulls (Larus argentatus) are exposed to contaminants from aquatic, terrestrial and anthropogenic sources. We aim to assess if differences in urbanisation affect ecological niche and contaminant concentrations in female herring gulls. Furthermore, we investigated maternal transfer from mothers to eggs for all the target compounds, including chlorinated paraffins (CPs) and cyclic volatile methyl siloxane (cVMSs), which to our knowledge have not been assessed in herring gulls previously. We compare concentrations of legacy and emerging contaminants and metals in blood and eggs between two herring gull colonies located 51 km apart, in the urban influenced Norwegian Oslofjord. While both colonies are within an urbanised area, the inner fjord is more so, as it is surrounded by Oslo, the capital and largest city in Norway Stable isotopes of carbon and nitrogen indicated a more marine ecological niche in the outer than the inner fjord colony, although with overlap. Persistent organic pollutant (POP) concentrations were similar in the inner and outer fjord colonies, while the short-chained chlorinated paraffins (SCCP), which are recently added to the Stockholm convention and contaminants of emerging concern (CECs) varied, with higher concentrations of SCCP and the cVMS decamethylcyclopentasiloxane (D5) in females and eggs of the inner fjord colony. Per- and polyfluorinated substances (PFAS) concentrations were higher in the outer fjord colony, likely linked to releases from a point-source (airport and waste management facility with open access to food waste). In blood, chlorinated paraffins contributed most the total lipophilic contaminants (inner: 78%, outer: 56%), while polychlorinated biphenyls (PCBs) were the most abundant lipophilic contaminants in eggs (inner: 62%, outer: 46%). Dechloranes and brominated flame retardants (BFRs) were detected in few samples. Maternal transfer, assessed by egg to blood ratios, of cVMSs were similar to the POPs with mean log ratio 0.39 (D5), while it was lower for SCCPs, with log ratios-0.77. Our results indicate comparable POP exposure of the herring gulls in the inner and outer Oslofjord, likely due to overlap in ecological niches between the colonies and wide distribution of POPs. The differences between the colonies in concentrations of PFAS, cVMS and CPs shows that point source exposures and urban influence may be more important than ecological niche for these compounds.

Gulls (Larus spp.) are described as generalist, opportunistic feeders that show great flexibility in habitat use. Despite an apparent advantage in changing landscapes, many Larus populations have declined in eastern North America since the 1990s. The main hypothesis explaining gull declines at a broad scale is a decrease in total food availability, especially anthropogenically derived fisheries discards and human refuse as industries and cities have improved their management practices. However, it is difficult to quantify the total proportion of gull diet subsidized by humans to test this hypothesis because many common prey items can be traced to both anthropogenic and nonanthropogenic sources. Our aim was to estimate the proportion of diet derived from anthropogenic food sources for Herring Gull (L. argentatus) during the breeding season at the two largest colonies in the Bay of Fundy, Canada, which are located 36 km apart. GPS loggers were deployed to quantify spatiotemporal movement patterns, and whole blood and feather samples were collected for δ13C and δ15N stable-isotope analysis to estimate diet composition during the incubation and chick-rearing stages of the breeding season. Results indicate that there is spatial segregation in the foraging areas used by gulls from the two colonies. All gulls relied on a variety of anthropogenic food sources, with some individuals selecting heavily on fisheries (i.e., active town wharfs, fish packaging plants, aquaculture pens) and mink (Neovison vison) fur farms. Landfills were not a significant source of food during the breeding season. Our study provides valuable information about the relative reliance of gulls on anthropogenic food subsidies, providing insight into how changing industry practices may affect patterns in nesting and foraging by gulls in the region.

Methylmercury concentrations vary widely across geographic space and among habitat types, with marine and aquatic-feeding organisms typically exhibiting higher mercury concentrations than terrestrial-feeding organisms. However, there are few model organisms to directly compare mercury concentrations as a result of foraging in marine, estuarine, or terrestrial food webs. The ecological impacts of differential foraging may be especially important for generalist species that exhibit high plasticity in foraging habitats, locations, or diet. Here, we investigate whether foraging habitat, sex, or fidelity to a foraging area impact blood mercury concentrations in western gulls (Larus occidentalis) from three colonies on the US west coast. Cluster analyses showed that nearly 70% of western gulls foraged primarily in ocean or coastal habitats, whereas the remaining gulls foraged in terrestrial and freshwater habitats. Gulls that foraged in ocean or coastal habitats for half or more of their foraging locations had 55% higher mercury concentrations than gulls that forage in freshwater and terrestrial habitats. Ocean-foraging gulls also had lower fidelity to a specific foraging area than freshwater and terrestrial-foraging gulls, but fidelity and sex were unrelated to gull blood mercury concentrations in all models. These findings support existing research that has described elevated mercury levels in species using aquatic habitats. Our analyses also demonstrate that gulls can be used to detect differences in contaminant exposure over broad geographic scales and across coarse habitat types, a factor that may influence gull health and persistence of other populations that forage across the land-sea gradient.

Understanding changes in environmental mercury concentrations is important for assessing the risk to human and wildlife populations from this potent toxicant. Here, we use herring gull (Larus argentatus) eggs to evaluate temporal changes in total mercury (THg) availability from two locations on Great Slave Lake (GSL), Northwest Territories, Canada. Egg THg concentrations increased through time, but this change was due to shifts in gull diets. Stable nitrogen isotopes allowed adjustment of egg THg concentrations for dietary changes. Diet-adjusted egg THg concentrations showed no long-term trend. Consistent with that result, new statistical analysis of THg concentrations in three species of GSL fish showed minor or no temporal changes. Although a long-term trend was absent, inter-year differences in adjusted egg THg concentrations persisted. Contributions of environmental variables (i.e., river flow, lake level, air temperature, precipitation, and wildfire) to these differences were investigated. Egg THg concentrations were greater following years of lower lake levels and greater wildfire extent. Lake level could have affected mercury methylation. Increased wildfire could have enhanced terrestrial Hg releases to the atmosphere where it was transported long distances to GSL. Climate change may increase wildfire extent with impacts on Hg bioaccumulation in northern ecosystems. Egg Hg levels reported here are unlikely to pose health risks to gulls, but in light of ongoing environmental change, monitoring should continue. Our study emphasizes the importance of ancillary datasets in elucidating Hg trends; such information will be critical for evaluating the effectiveness of Hg mitigation strategies implemented as part of the Minamata Convention.

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.

Interactions between urban wildlife and people are increasing globally. Some of these interactions can be negative and lead to human-wildlife conflicts. In St Andrews, Scotland, residents and business owners have come into conflict with herring gulls (Larus argentatus) and lesser black-backed gulls (Larus fuscus) that nest and forage in the town. This study quantified the number, species and distribution of nesting gulls; the vulnerability of different sources of rubbish to attack; and the likelihood of negative human-gull interactions related to food. Surveys were conducted in St Andrews during the 2016 breeding season (May-July). Nesting gull density and distribution were estimated during weekly street surveys of buildings; vantage surveys were conducted for some buildings and a correction factor estimating a minimum number of nesting gulls was produced. 110 nesting gull pairs were estimated and these occupied ~10% of buildings. The vulnerability of waste sources to attack was monitored during transects recording whether or not rubbish sources were attacked. Black bin bags had the highest probability of being attacked, but placing these in secured hessian bags prevented this. The frequency of negative human-gull interactions involving food at street-level was determined during 10-minute timed watches at various locations. Incidences of gulls taking food were rare; only eight were seen in 30 hours of watches. Altering human behaviour (for example, disposing of waste securely) will mitigate potential issues with urban wildlife. Findings from this study will enable effective management of human-gull conflicts in St Andrews and have potential applications in other urban communities.

espanolLa costa vasca constituye un area de paso e invernada de gaviotas en el Golfo de Vizcaya y este a su vez en el Paleartico sudoccidental. Este trabajo se establece con el fin de determinar la importancia relativa de las especies que frecuentan la region en invierno, estimar su abundancia, identificar las zonas mas importantes y evaluar hasta que punto un censo unico representa bien la abundancia de gaviotas de un invierno. Estructuralmente, hay dos tipos de estuarios en la costa vasca: aquellos en los que la gaviota reidora Chroicocephalus ridibundus (L. 1766) muestra niveles de abundancia relativa comparables a los de la gaviota patiamarilla Larus michahellis Naumann 1840 y aquellos en los que domina esta ultima, que por otro lado acumula el 66,5% de la abundancia de gaviotas en la costa vasca. La estima de la abundancia basada en un modelo log-lineal aporto un valor medio de unas 4500 gaviotas para el invierno de 2019/20 (con una probabilidad al 95% de que el valor real se situe en el rango de 2500 a 7500 gaviotas). En cuanto a las zonas mas importantes de la region para la invernada de gaviotas, destacan Donostia, Txingudi, Urdaibai y Ondarroa. Observamos, ademas, un incremento de la abundancia en dias lluviosos respecto a los no lluviosos, si bien este efecto se diluye ante la enorme variabilidad asociada a cada zona de muestreo. Esto supone que las cifras son altamente variables, tanto si consideramos el conjunto de especies como cada una de las mas frecuentes por separado. Ante esta realidad, se concluye que los resultados de un unico censo no representan las abundancias de las gaviotas que invernan en la costa vasca, por lo que se recomienda llevar a cabo varios censos simultaneos con el fin de estimar un valor medio junto a su incertidumbre asociada. euskaraEuskal kostaldea kaioen eta antxeten paserako eta negua igarotzeko eremua da Bizkaiko Golkoan, eta azken honek funtzio bera betetzen du Mendebaldeko Paleartikoan. Burutu dugun lanaren helburuak izan dira eremu honetan neguan aurki daitezkeen espezieen garrantzi erlatiboa zehaztea, horien ugaritasuna kalkulatzea, zonalde garrantzitsuenak identifikatzea eta kaioen ugaritasuna kalkulatzeko zentso bakar baten egokitasuna ebaluatzea. Egiturari dagokionez, bi motatako estuarioak aurki ditzakegu euskal kostaldean: batetik, antxeta mokogorriaren Chroicocephalus ridibundus (L. 1766) eta kaio hankahoriaren Larus michahellis Naumann 1840 ugaritasun erlatibo antzekoak dituzten estuarioak; eta, bestetik, kaio hankahoriaren, zeinak euskal kostaldeko kaioen %66,5 osatzen duen, ugaritasun erlatibo handiagoa dutenak. Log-lineala ereduan oinarritutako ugaritasun-estimazioak batezbesteko 4500 aleko balioa eman zuen 2019/20 negurako (kaioen kopuru erreala 2500-7500 balioen artean egoteko % 95eko probabilitatearekin). Negua igarotzeko erabilitako eskualdeei dagokienez, Donostia, Txingudi, Urdaibai eta Ondarroa zonalde garrantzitsu gisa nabarmendu dira. Egindako behaketen arabera, euririk gabeko egunekin alderatuz, egun euritsuetan ugaritasuna hazi egiten da. Alabaina, laginketa-eremuen aldakortasun handia dela-eta efektu horrek indarra galtzen du. Horregatik, jasotako zenbatekoak ere oso aldakorrak izan ohi dira, bai espezie-multzo osoa kontuan izanda, bai maiztasun handieneko espezie bakoitza bere aldetik kontuan hartuta ere. Hori dela eta, zera ondorioztatu da: zentsu bakar bateko emaitzak ez direla esanguratsuak euskal kostaldean negua pasatzen duten kaio eta antxeten ugaritasuna neurtzeko; eta, ondorioz, aldibereko hainbat kontaketa burutzea gomendatzen da, batezbesteko balio bat estimatu ahal izateko, balio horri lotutako ziurgabetasunarekin batera EnglishThe Basque coast is a migratory and wintering area for several gull species within the Gulf of Biscay and the Southwestern Palaearctic. This paper aims to assess the relative importance of those species that overwinter along this coast, estimate their abundance, identify the main areas and evaluate to what extent a single census is enough to represent their abundance. Structurally, we found two types of estuaries: those in which the black-headed gull Chroicocephalus ridibundus (L. 1766) co-dominated with the yellow-legged gull Larus michahellis Naumann 1840, and those in which the yellow-legged gull was dominant. The latter species accounted for 66.5% of the overall gull population size within the Basque coast. The mean gull population size determined by a log-linear model for all species was 4500 individuals for the winter 2019/20 (95% CI: 2500-7500 gulls). The main locations within the region were Donostia, Txingudi, Urdaibai and Ondarroa. We observed an increasing number of counts on rainy days as compared to dry days but this effect was very small as compared to the high variance associated with each survey locality. In view of such a high variability, it can be concluded that the results from a single census are not enough to estimate the population size of those gulls overwintering within the region. Several censuses throughout the winter are recommended to obtain a more robust estimate

International audience; Studies of model animals like mice and rats have led to great advances in our understanding of the process of tumorigenesis, but this line of study has less to offer for understanding the mechanisms of cancer resistance. Increasing the diversity of nonmodel species from the perspective of molecular mechanisms of natural cancer resistance can lead to new insights into the evolution of protective mechanisms against neoplastic processes and to a wider understanding of natural cancer defense mechanisms. Such knowledge could then eventually be harnessed for the development of human cancer therapies. We suggest here that seabirds are promising, albeit currently completely ignored candidates for studying cancer defense mechanisms, as they have a longer maximum life span than expected from their body size and rates of energy metabolism and may have thus evolved mechanisms to limit neoplasia progression, especially at older ages. We here apply a novel, intraspecific approachof comparing old and young seabirds for improving our understanding of aging and neoplastic processes in natural settings. We used the long-lived common gulls (Larus canus) for studying the age-related pattern of expression of cancer-related genes, based on transcriptome analysis and databases of orthologues of human cancer genes. The analysis of differently expressed cancer-related genes between young and old gulls indicated that similarly to humans, age is potentially affecting cancer risk in this species. Out of eleven differentially expressed cancer-related genes between the groups, three were likely artifactually linked to cancer. The remaining eight were downregulated in old gulls compared to young ones. The downregulation of five of them could be interpreted as a mechanism suppressing neoplasia risk and three as increasing the risk. Based on these results, we suggest that old gulls differ from young ones both from the aspect of cancer susceptibility and tumor suppression atthe genetic level.

Migratory birds are potential vehicles of antibiotic-resistant bacteria. In this study, a colistin-resistant Escherichia coli strain, CLR8, was isolated from the feces of Larus argentatus. The draft genome sequence of the strain indicated that it hosts mcr-1, which is a plasmid-mediated colistin resistance gene.

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 Gulls Larus 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.

Background Recent studies have proposed that birds migrating short distances migrate at an overall slower pace, minimizing energy expenditure, while birds migrating long distances minimize time spent on migration to cope with seasonal changes in environmental conditions. Methods We evaluated variability in the migration strategies of Herring Gulls (Larus argentatus), a generalist species with flexible foraging and flight behaviour. We tracked one population of long distance migrants and three populations of short distance migrants, and compared the directness of their migration routes, their overall migration speed, their travel speed, and their use of stopovers. Results Our research revealed that Herring Gulls breeding in the eastern Arctic migrate long distances to spend the winter in the Gulf of Mexico, traveling more than four times farther than gulls from Atlantic Canada during autumn migration. While all populations used indirect routes, the long distance migrants were the least direct. We found that regardless of the distance the population traveled, Herring Gulls migrated at a slower overall migration speed than predicted by Optimal Migration Theory, but the long distance migrants had higher speeds on travel days. While long distance migrants used more stopover days overall, relative to the distance travelled all four populations used a similar number of stopover days. Conclusions When taken in context with other studies, we expect that the migration strategies of flexible generalist species like Herring Gulls may be more influenced by habitat and food resources than migration distance.

Expansion of marine aquaculture into more remote areas will likely accelerate over the next decade. Integrating Marine Renewable Energy (MRE) generation technologies (e.g., wind turbines) into remote, off-grid aquaculture sites will reduce reliance on fossil fuels by allowing localised low-carbon power generation, but may also result in novel environmental pressures. In this study, we undertook a thought experiment to assess the potential for increased collision risks to local marine and coastal bird species of integrating small wind turbines (4 units, combined capacity of 200 MWh) into a generalised marine fish farm in western Scotland (UK). Potential risks to bird species were assessed using a bespoke Sensitivity Index (SI) based on 12 factors, including population size, adult survival rate, UK conservation status, flight manoeuvrability, nocturnal flight activity, habitat preference, sensitivity to wind farms, attraction to fish farms for feeding and/or resting, and attraction to other marine anthropogenic structures/activities. SI scores varied substantially between species, but large gulls (Larus sp.) and European shag (Phalacrocorax aristotelis) were expected to be at the greatest potential risk. The general lack of information on interactions between birds and fish farms represented a significant knowledge gap, and greater focus on these interactions is needed to improve future risk assessments.

Naturally occurring radionuclides, in particular, polonium-210 (210Po), have a greater contribution than anthropogenic radionuclides to the annual effective dose received by the general public due to consumption of seafood. Knowledge of potential trophic sources and transfer of 210Po to seabird species and subsequently to the Greenlandic people is, however, still poor. Here, we assess the transfer of 210Po and 210Pb to seabirds sampled during autumn and winter 2017 and 2018 in Greenland and provide a dose assessment. The activity concentrations of 210Po in muscle and liver, respectively, ranged from 0.2 ± 0.1 Bq kg−1 w.w. in glaucous gull (Larus hyperboreus) to 21.2 ± 22.6 Bq kg−1 w.w. in thick-billed murre (Uria lomvia) and from 32.0 ± 9.4 Bq kg−1 w.w. in common eider (Somateria mollissima) to 40.5 ± 49.0 Bq kg−1 w.w. in thick-billed murre. 210Po was non-uniformly distributed in the body of thick-billed murre. Kidneys and feathers showed higher 210Po activity concentrations than heart and bone. The 210Po/210Pb activity concentration ratios are higher than unity, indicating that 210Po is preferentially taken up by seabirds compared to its progenitor 210Pb. The derived annual absorbed dose from 210Po to the whole body of thick-billed murre was 6.4 × 102 ± 3.0 × 102 μGy. The annual effective dose to the average adult and representative person in Greenland due to ingestion of 210Po in seabirds was estimated to 13.0 μSv and 57.0 μSv, respectively. This derived dose is low and poses a slight risk, and risk communication is therefore deemed unnecessary.

International audience; Capital breeders accumulate nutrients prior to egg development, then use these stores to support offspring development. In contrast, income breeders rely on local nutrients consumed contemporaneously with offspring development. Understanding such nutrient allocations is critical to assessing life‐history strategies and habitat use. Despite the contrast between these strategies, it remains challenging to trace nutrients from endogenous stores or exogenous food intake into offspring. Here, we tested a new solution to this problem. Using tissue samples collected opportunistically from wild emperor penguins Aptenodytes forsteri, which exemplify capital breeding, we hypothesized that the stable carbon (δ13C) and nitrogen (δ15N) isotope values of individual amino acids (AAs) in endogenous stores (e.g. muscle) and in egg yolk and albumen reflect the nutrient sourcing that distinguishes capital versus income breeding. Unlike other methods, this approach does not require untested assumptions or diet sampling. We found that over half of essential AAs had δ13C values that did not differ between muscle and yolk or albumen, suggesting that most of these AAs were directly routed from muscle into eggs. In contrast, almost all non‐essential AAs differed in δ13C values between muscle and yolk or between muscle and albumen, suggesting de novo synthesis. Over half of AAs that have labile nitrogen atoms (i.e. ‘trophic’ AA) had higher δ15N values in yolk and albumen than in muscle, suggesting that they were transaminated during their routing into egg tissue. This effect was smaller for AAs with less labile nitrogen atoms (i.e. ‘source’ AA). Our results indicate that the δ15N offset between trophic‐source AAs (Δ15Ntrophic‐source) may provide an index of the extent of capital breeding. The value of emperor penguin Δ15NPro‐Phe was higher in yolk and albumen than in muscle, reflecting the mobilization of endogenous stores; in comparison, the value of Δ15NPro‐Phe was similar across muscle and egg tissue in previously published data for income‐breeding herring gulls Larus argentatus smithsonianus. Our results provide a quantitative basis for using AA δ13C and δ15N, and isotopic offsets among AAs (e.g. Δ15NPro‐Phe), to explore the allocation of endogenous versus exogenous nutrients across the capital versus income spectrum of avian reproduction.