Seabirds reveal mercury distribution across the North Atlantic.

Mercury (Hg) is a heterogeneously distributed toxicant affecting wildlife and human health. Yet, the spatial distribution of Hg remains poorly documented, especially in food webs, even though this knowledge is essential to assess large-scale risk of toxicity for the biota and human populations. Here, we used seabirds to assess, at an unprecedented population and geographic magnitude and high resolution, the spatial distribution of Hg in North Atlantic marine food webs. To this end, we combined tracking data of 837 seabirds from seven different species and 27 breeding colonies located across the North Atlantic and Atlantic Arctic together with Hg analyses in feathers representing individual seabird contamination based on their winter distribution. Our results highlight an east-west gradient in Hg concentrations with hot spots around southern Greenland and the east coast of Canada and a cold spot in the Barents and Kara Seas. We hypothesize that those gradients are influenced by eastern (Norwegian Atlantic Current and West Spitsbergen Current) and western (East Greenland Current) oceanic currents and melting of the Greenland Ice Sheet. By tracking spatial Hg contamination in marine ecosystems and through the identification of areas at risk of Hg toxicity, this study provides essential knowledge for international decisions about where the regulation of pollutants should be prioritized.

An ecologically sound and participatory monitoring network for pan-Arctic seabirds.

In a warming Arctic, circumpolar long-term monitoring programs are key to advancing ecological knowledge and informing environmental policies. Calls for better involvement of Arctic peoples in all stages of the monitoring process are widespread, although such transformation of Arctic science is still in its infancy. Seabirds stand out as ecological sentinels of environmental changes, and priority has been given to implement the Circumpolar Seabird Monitoring Plan (CSMP). We assessed the representativeness of a pan-Arctic seabird monitoring network focused on the black-legged kittiwake (Rissa tridactyla) by comparing the distribution of environmental variables for all known versus monitored colonies. We found that with respect to its spatiotemporal coverage, this monitoring network does not fully embrace current and future environmental gradients. To improve the current scheme, we designed a method to identify colonies whose inclusion in the monitoring network will improve its ecological representativeness, limit logistical constraints, and improve involvement of Arctic peoples. We thereby highlight that inclusion of study sites in the Bering Sea, Siberia, western Russia, northern Norway, and southeastern Greenland could improve the current monitoring network and that their proximity to local populations might allow increased involvement of local communities. Our framework can be applied to improve existing monitoring networks in other ecoregions and sociological contexts.

Una red de monitoreo participativa y ecológica para las aves marinas del Ártico Resumen En un Ártico cada vez más cálido, los programas circumpolares de monitoreo a largo plazo son importantes para potenciar el conocimiento ecológico e informar las políticas ambientales. Existe un llamado generalizado para involucrar de mejor manera a los pueblos árticos en el proceso de monitoreo, aunque dicha transformación de la ciencia ártica todavía está en desarrollo. Las aves marinas resaltan como centinelas del cambio ambiental y se ha priorizado implementar el Plan Circumpolar de Monitoreo de Aves Marinas (CSMP). Comparamos la distribución de las variables ambientales de todas las colonias conocidas de la gaviota tridáctila (Rissa tridactyla) contra las colonias monitoreadas para evaluar la representación de una red pan­ártica de monitoreo enfocada en esta especie. Encontramos que esta red de monitoreo no considera del todo los gradientes ambientales actuales y futuros con respecto a la cobertura espaciotemporal. Para mejorar el esquema actual, diseñamos un método para identificar las colonias cuya inclusión en la red de monitoreo mejorará su representación ecológica, limitará las restricciones logísticas e incrementará la participación de los pueblos árticos. Por lo tanto, resaltamos que la inclusión de los sitios de estudio en el Mar de Bering, Siberia, Rusia occidental, el norte de Noruega y el sureste de Groenlandia mejorarían la red actual de monitoreo. También destacamos que la proximidad de los sitios de estudio con las poblaciones locales podría permitir una mayor participación de estas. Nuestro marco puede aplicarse para mejorar las redes de monitoreo existentes en otros contextos socioecológicos y ecoregiones.

Searching for genetic evidence of demographic decline in an arctic seabird: beware of overlapping generations.

Genetic data are useful for detecting sudden population declines in species that are difficult to study in the field. Yet this indirect approach has its own drawbacks, including population structure, mutation patterns, and generation overlap. The ivory gull (Pagophila eburnea), a long-lived Arctic seabird, is currently suffering from rapid alteration of its primary habitat (i.e., sea ice), and dramatic climatic events affecting reproduction and recruitment. However, ivory gulls live in remote areas, and it is difficult to assess the population trend of the species across its distribution. Here we present complementary microsatellite- and SNP-based genetic analyses to test a recent bottleneck genetic signal in ivory gulls over a large portion of their distribution. With attention to the potential effects of population structure, mutation patterns, and sample size, we found no significant signatures of population decline worldwide. At a finer scale, we found a significant bottleneck signal at one location in Canada. These results were compared with predictions from simulations showing how generation time and generation overlap can delay and reduce the bottleneck microsatellite heterozygosity excess signal. The consistency of the results obtained with independent methods strongly indicates that the species shows no genetic evidence of an overall decline in population size. However, drawing conclusions related to the species' population trends will require a better understanding of the effect of age structure in long-lived species. In addition, estimates of the effective global population size of ivory gulls were surprisingly low (~1000 ind.), suggesting that the evolutionary potential of the species is not assured.

Meeting Paris agreement objectives will temper seabird winter distribution shifts in the North Atlantic Ocean.

We explored the implications of reaching the Paris Agreement Objective of limiting global warming to <2°C for the future winter distribution of the North Atlantic seabird community. We predicted and quantified current and future winter habitats of five North Atlantic Ocean seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla) using tracking data for ~1500 individuals through resource selection functions based on mechanistic modeling of seabird energy requirements, and a dynamic bioclimate envelope model of seabird prey. Future winter distributions were predicted to shift with climate change, especially when global warming exceed 2°C under a "no mitigation" scenario, modifying seabird wintering hotspots in the North Atlantic Ocean. Our findings suggest that meeting Paris agreement objectives will limit changes in seabird selected habitat location and size in the North Atlantic Ocean during the 21st century. We thereby provide key information for the design of adaptive marine-protected areas in a changing ocean.

Contrasting Spatial and Seasonal Trends of Methylmercury Exposure Pathways of Arctic Seabirds: Combination of Large-Scale Tracking and Stable Isotopic Approaches.

Despite the limited direct anthropogenic mercury (Hg) inputs in the circumpolar Arctic, elevated concentrations of methylmercury (MeHg) are accumulated in Arctic marine biota. However, the MeHg production and bioaccumulation pathways in these ecosystems have not been completely unraveled. We measured Hg concentrations and stable isotope ratios of Hg, carbon, and nitrogen in the feathers and blood of geolocator-tracked little auk Alle alle from five Arctic breeding colonies. The wide-range spatial mobility and tissue-specific Hg integration times of this planktivorous seabird allowed the exploration of their spatial (wintering quarters/breeding grounds) and seasonal (nonbreeding/breeding periods) MeHg exposures. An east-to-west increase of head feather Hg concentrations (1.74-3.48 µg·g-1) was accompanied by significant spatial trends of Hg isotope (particularly Δ199Hg: 0.96-1.13‰) and carbon isotope (δ13C: -20.6 to -19.4‰) ratios. These trends suggest a distinct mixing/proportion of MeHg sources between western North Atlantic and eastern Arctic regions. Higher Δ199Hg values (+0.4‰) in northern colonies indicate an accumulation of more photochemically impacted MeHg, supporting shallow MeHg production and bioaccumulation in high Arctic waters. The combination of seabird tissue isotopic analysis and spatial tracking helps in tracing the MeHg sources at various spatio-temporal scales.

Diverging phenological responses of Arctic seabirds to an earlier spring.

The timing of annual events such as reproduction is a critical component of how free-living organisms respond to ongoing climate change. This may be especially true in the Arctic, which is disproportionally impacted by climate warming. Here, we show that Arctic seabirds responded to climate change by moving the start of their reproduction earlier, coincident with an advancing onset of spring and that their response is phylogenetically and spatially structured. The phylogenetic signal is likely driven by seabird foraging behavior. Surface-feeding species advanced their reproduction in the last 35 years while diving species showed remarkably stable breeding timing. The earlier reproduction for Arctic surface-feeding birds was significant in the Pacific only, where spring advancement was most pronounced. In both the Atlantic and Pacific, seabirds with a long breeding season showed a greater response to the advancement of spring than seabirds with a short breeding season. Our results emphasize that spatial variation, phylogeny, and life history are important considerations in seabird phenological response to climate change and highlight the key role played by the species' foraging behavior.

Earlier colony arrival but no trend in hatching timing in two congeneric seabirds (Uria spp.) across the North Atlantic.

A global analysis recently showed that seabird breeding phenology (as the timing of egg-laying and hatching) does not, on average, respond to temperature changes or advance with time (Keogan et al. 2018 Nat. Clim. Change8, 313-318). This group, the most threatened of all birds, is therefore prone to spatio-temporal mismatches with their food resources. Yet, other aspects of the breeding phenology may also have a marked influence on breeding success, such as the arrival date of adults at the breeding site following winter migration. Here, we used a large tracking dataset of two congeneric seabirds breeding in 14 colonies across 18° latitudes, to show that arrival date at the colony was highly variable between colonies and species (ranging 80 days) and advanced 1.4 days/year while timing of egg-laying remained unchanged, resulting in an increasing pre-laying duration between 2009 and 2018. Thus, we demonstrate that potentially not all components of seabird breeding phenology are insensitive to changing environmental conditions.

Flexibility of foraging strategies of the great skua Stercorarius skua breeding in the largest colony in the Barents Sea region.

BACKGROUND: Foraging strategies of seabird species often vary considerably between and within individuals. This variability is influenced by a multitude of factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions. RESULTS: Using GPS-loggers, we investigated factors affecting foraging flight characteristics (total duration, maximal range, total distance covered) of great skuas Stercorarius skua of known sex breeding on Bjørnøya, Svalbard, the largest colony in the Barents Sea region. We examined influence of sex (females are larger than males), phase of breeding (incubation, chick-rearing), reproductive status (breeders, failed breeders) and bird ID (they are known for individual foraging specialization). Our analyses revealed that only bird ID affected foraging flight characteristics significantly, indicating a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized three main groups of individuals: 1) those preying mainly on other seabirds in the breeding colonies (6%), 2) those foraging at sea (76%) and kleptoparasiting other seabirds and/or foraging on fish and/or offal discarded by fishing vessels, and 3) those alternating between preying on other seabirds in breeding colonies and foraging at sea (18%). Despite marked size sexual dimorphism, we found no apparent sex differences in flight characteristics. Birds after egg- or chick-loss and thus not constrained as central foragers did not modify their foraging flights. CONCLUSIONS: Great skuas breeding on Bjørnøya displayed a high degree of plasticity regardless of sex, reproductive status or phase of breeding. We recognized groups of individuals regularly preying in the seabird colonies, foraging at sea, and alternating between both strategies. This suggests foraging specialization of some individuals.

Climate change impacts on wildlife in a High Arctic archipelago - Svalbard, Norway.

The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of 'rain-on-snow' events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore-predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long-term (multidecadal) demographic, population- and ecosystem-based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming.

Circumpolar dynamics of a marine top-predator track ocean warming rates.

Global warming is a nonlinear process, and temperature may increase in a stepwise manner. Periods of abrupt warming can trigger persistent changes in the state of ecosystems, also called regime shifts. The responses of organisms to abrupt warming and associated regime shifts can be unlike responses to periods of slow or moderate change. Understanding of nonlinearity in the biological responses to climate warming is needed to assess the consequences of ongoing climate change. Here, we demonstrate that the population dynamics of a long-lived, wide-ranging marine predator are associated with changes in the rate of ocean warming. Data from 556 colonies of black-legged kittiwakes Rissa tridactyla distributed throughout its breeding range revealed that an abrupt warming of sea-surface temperature in the 1990s coincided with steep kittiwake population decline. Periods of moderate warming in sea temperatures did not seem to affect kittiwake dynamics. The rapid warming observed in the 1990s may have driven large-scale, circumpolar marine ecosystem shifts that strongly affected kittiwakes through bottom-up effects. Our study sheds light on the nonlinear response of a circumpolar seabird to large-scale changes in oceanographic conditions and indicates that marine top predators may be more sensitive to the rate of ocean warming rather than to warming itself.

Living on the edge of a shrinking habitat: the ivory gull, Pagophila eburnea, an endangered sea-ice specialist.

The ongoing decline of sea ice threatens many Arctic taxa, including the ivory gull. Understanding how ice-edges and ice concentrations influence the distribution of the endangered ivory gulls is a prerequisite to the implementation of adequate conservation strategies. From 2007 to 2013, we used satellite transmitters to monitor the movements of 104 ivory gulls originating from Canada, Greenland, Svalbard-Norway and Russia. Although half of the positions were within 41 km of the ice-edge (75% within 100 km), approximately 80% were on relatively highly concentrated sea ice. Ivory gulls used more concentrated sea ice in summer, when close to their high-Arctic breeding ground, than in winter. The best model to explain the distance of the birds from the ice-edge included the ice concentration within approximately 10 km, the month and the distance to the colony. Given the strong links between ivory gull, ice-edge and ice concentration, its conservation status is unlikely to improve in the current context of sea-ice decline which, in turn, will allow anthropogenic activities to develop in regions that are particularly important for the species.

Trace Element Concentrations in Relation to the Trophic Behaviour of Endangered Ivory Gulls (Pagophila eburnea) During Their Stay at a Breeding Site in Svalbard.

The ivory gull is a high-Arctic species considered endangered in most parts of its breeding range. Ivory gulls must cope with both the reduction of sea ice cover triggered by climate change and increasing contaminant loads due to changes in global contaminant pathways. The objective of this study was to assess the concentration of 14 essential and nonessential trace elements at four colonies of ivory gulls breeding on Barentsøya, Svalbard, and the relationship between contaminant exposure and the diet of individuals. Contaminants and stable isotopes (δ15N, δ13C) were determined in blood (red blood cells and whole blood), and feathers of ivory gulls collected over several years. The most quantitatively abundant nonessential trace element found in the ivory gull was mercury (Hg). Selenium (Se) was present in substantial surplus compared with Hg, which would imply relative protection against Hg toxic effects but raises concern about Se potential toxicity. Moreover, other elements were detected, such as silver, arsenic, cadmium, and lead, which would warrant monitoring because of the potential additive/synergetic effects of these compounds. This study demonstrated individual differences in trophic behaviour that triggered discrepancies in Hg concentrations, highlighting the potential biomagnifying ability of this metal in the ivory gull's food web. Results highlighted the mixing of birds coming from different geographical areas on Barentsøya.

Spatial distribution of selenium-mercury in Arctic seabirds.

Mercury (Hg) is a metallic trace element toxic for humans and wildlife that can originate from natural and anthropic sources. Hg spatial gradients have been found in seabirds from the Arctic and other oceans, suggesting contrasting toxicity risks across regions. Selenium (Se) plays a protective role against Hg toxicity, but its spatial distribution has been much less investigated than that of Hg. From 2015 to 2017, we measured spatial co-exposure of Hg and Se in blood samples of two seabird species, the Brünnich's guillemot (Uria lomvia) and the black-legged kittiwake (Rissa tridactyla) from 17 colonies in the Arctic and subarctic regions, and we calculated their molar ratios (Se:Hg), as a measure of Hg sequestration by Se and, therefore, of Hg exposure risk. We also evaluated concentration differences between species and ocean basins (Pacific-Arctic and Atlantic-Arctic), and examined the influence of trophic ecology on Hg and Se concentrations using nitrogen and carbon stable isotopes. In the Atlantic-Arctic ocean, we found a negative west-to-east gradient of Hg and Se for guillemots, and a positive west-to-east gradient of Se for kittiwakes, suggesting that these species are better protected from Hg toxicity in the European Arctic. Differences in Se gradients between species suggest that they do not follow environmental Se spatial variations. This, together with the absence of a general pattern for isotopes influence on trace element concentrations, could be due to foraging ecology differences between species. In both oceans, the two species showed similar Hg concentrations, but guillemots showed lower Se concentrations and Se:Hg than kittiwakes, suggesting a higher Hg toxicity risk in guillemots. Within species, neither Hg, nor Se or Se:Hg differed between both oceans. Our study highlights the importance of considering Se together with Hg, along with different species and regions, when evaluating Hg toxic effects on marine predators in international monitoring programs.

Persistent organic pollution in a high-Arctic top predator: sex-dependent thresholds in adult survival.

In long-lived species, any negative effect of pollution on adult survival may pose serious hazards to breeding populations. In this study, we measured concentrations of various organochlorines (OCs) (polychlorinated biphenyl and OC pesticides) in the blood of a large number of adult glaucous gulls (Larus hyperboreus) breeding on Bjørnøya (Bear Island) in the Norwegian Arctic, and modelled their local survival using capture-recapture analysis. Survival was negatively associated with concentrations of OCs in the blood. The effect of OCs was nonlinear and evident only among birds with the highest concentrations (the uppermost deciles of contamination). The threshold for depressed survival differed between the sexes, with females being more sensitive to contamination. For birds with lower OC concentration, survival was very high, i.e. at the upper range of survival rates reported from glaucous and other large gull species in other, presumably less contaminated populations. We propose two non-exclusive explanations. First, at some threshold of OC concentration, parents (especially males) may abandon reproduction to maximize their own survival. Second, high contamination of OC may eliminate the most sensitive individuals from the population (especially among females), inducing a strong selection towards high-quality and less sensitive phenotypes.

Decline of an arctic top predator: synchrony in colony size fluctuations, risk of extinction and the subpolar gyre.

Analysis of synchrony in population fluctuations is a central topic in ecology. It can help identify factors that regulate populations, and also the scales at which these factors exert their influence. Using long-term data from seven Brünnich's guillemot colonies in Svalbard, Norway, we determined that year to year population fluctuations were synchronized in six of the seven colonies. The seventh colony was located farther away and in a different oceanographic system. Moreover, all seven colonies have declined significantly since the late 1990s following a very similar pattern. If the rate of population decline does not change, Brünnich's guillemots in Svalbard have a high probability of becoming quasi-extinct within the next 50 years. The high synchrony between the different colonies could further increase this risk of extinction. Our results indicate that environmental forcing plays a role in the colony size fluctuation of Brünnich's guillemot (i.e., a Moran effect). These fluctuations are well explained by changes in the subpolar gyre in the region where Brünnich's guillemots overwinter. This subpolar gyre weakened in the mid-1990s, leading to a warming of the North Atlantic. Our study indicates that this basin-scale shift in the subpolar gyre is closely related to the decline in Brünnich's guillemot in Svalbard. Our results suggest that the causal mechanism linking changes in oceanographic conditions in the North Atlantic and Brünnich's guillemot population dynamics are likely mediated, at least partly, by changes in recruitment.

Organohalogen contaminants and Blood plasma clinical-chemical parameters in three colonies of North Atlantic Great skua (Stercorarius skua).

The present study compares blood plasma clinical-chemical parameters (BCCPs) in birds from three geographically distinct North Atlantic Great skua (Stercorarius skua) colonies. Birds from these sites bioaccumulate different POP (persistent organic pollutant) concentrations and that enabled us to compare Great skua BCCPs in different exposure scenarios. Persistent organic pollutants (organochlorines: PCB, DDT, chlordanes, HCB, HCH, mirex and brominated flame retardants: PBDEs) and nineteen BCCPs were analysed in 114 adult Great skuas sampled during summer 2009 in North Atlantic colonies at Bjørnøya (n=42), Iceland (n=57) and Shetland (n=15). Specimens from Bjørnøya had the highest blood plasma concentrations of all contaminant groups followed by Iceland and Shetland birds, respectively (ANOVA: p<0.05). Most of the 19 BCCP parameters followed the pattern of colony differences found for contaminants, with Bjørnøya having the highest concentrations. However seven BCCPs, the three liver enzymes ALKP, ALAT and GGT as well as bile acids, cholesterol, sodium and potassium, did not differ between colonies (ANOVA: p>0.05). Therefore correlation analyses of these seven BCCPs vs. POPs were done on the combined colony data while the analyses of the remaining 12 BCCPs were carried out for each colony separately. The analyses of combined colony data showed that the blood plasma concentration of liver enzymes ALAT and GGT increased with increasing concentrations of ΣPBDE and ΣHCH, HCB and ΣCHL, respectively (all Pearson's p<0.05). In Great skuas from Shetland, the important osmotic transport protein albumin increased with increasing concentrations of ΣPCB and ΣDDT, while total blood plasma protein increased with ΣPCB, ΣDDT, ΣHCH and HCB concentrations (all Pearson's p<0.05). In both Bjørnøya and Iceland skuas, blood plasma pancreatic enzyme amylase decreased with increasing ΣHCH concentrations while the erythrocyte waste product total bilirubin in blood plasma increased with increasing ΣHCH and ΣPBDE concentrations in Iceland Great skuas (all Pearson's p<0.05). In Bjørnøya birds, blood plasma urea from protein metabolism (reflects kidney function) increased with increasing ΣPBDE concentrations (Pearson's p<0.05). Furthermore, a redundancy analysis showed that 10.6% of the variations in BCCPs could be explained by the variations in POP concentrations. Based on these results we suggest that liver and renal functions could be negatively affected by different POP compounds. It is, however, uncertain if the colony BCCP differences and their relationship to POP concentrations reflect health effects that could have an overall impact on the populations via reduced survival and reproduction parameters.

Use of geolocators for investigating breeding ecology of a rock crevice-nesting seabird: Method validation and impact assessment.

Investigating ecology of marine animals imposes a continuous challenge due to their temporal and/or spatial unavailability. Light-based geolocators (GLS) are animal-borne devices that provide relatively cheap and efficient method to track seabird movement and are commonly used to study migration. Here, we explore the potential of GLS data to establish individual behavior during the breeding period in a rock crevice-nesting seabird, the Little Auk, Alle alle. By deploying GLS on 12 breeding pairs, we developed a methodological workflow to extract birds' behavior from GLS data (nest attendance, colony attendance, and foraging activity), and validated its accuracy using behavior extracted from a well-established method based on video recordings. We also compared breeding outcome, as well as behavioral patterns of logged individuals with a control group treated similarly in all aspects except for the deployment of a logger, to assess short-term logger effects on fitness and behavior. We found a high accuracy of GLS-established behavioral patterns, especially during the incubation and early chick rearing period (when birds spend relatively long time in the nest). We observed no apparent effect of logger deployment on breeding outcome of logged pairs, but recorded some behavioral changes in logged individuals (longer incubation bouts and shorter foraging trips). Our study provides a useful framework for establishing behavioral patterns (nest attendance and foraging) of a crevice-nesting seabird from GLS data (light and conductivity), especially during incubation and early chick rearing period. Given that GLS deployment does not seem to affect the breeding outcome of logged individuals but does affect fine-scale behavior, our framework is likely to be applicable to a variety of crevice/burrow nesting seabirds, even though precautions should be taken to reduce deployment effect. Finally, because each species may have its own behavioral and ecological specificity, we recommend performing a pilot study before implementing the method in a new study system.

Decadal increase in vessel interactions by a scavenging pelagic seabird across the North Atlantic.

Fisheries waste is used by many seabirds as a supplementary source of food,1 but interacting with fishing vessels to obtain this resource puts birds at risk of entanglement in fishing gear and mortality.2 As a result, bycatch is one of the leading contributors to seabird decline worldwide,3 and this risk may increase over time as birds increasingly associate fishing vessels with food. Light-level geolocators mounted on seabirds can detect light emitted from vessels at night year-round.4 We used a 16-year time series of geolocator data from 296 northern fulmars (Fulmarus glacialis) breeding at temperate and arctic colonies to investigate trends of nocturnal vessel interactions in this scavenging pelagic seabird. Vessel attendance has progressively increased over the study period despite no corresponding increase in the number of vessels or availability of discards over the same time frame. Fulmars are highly mobile generalist surface feeders,5 so this may signal a reduction in available prey biomass in the upper water column, leading to increased reliance on anthropogenic food subsidies6 and increased risk of bycatch mortality in already threatened seabird populations. Individuals were consistent in the extent to which they interacted with vessels, as shown in other species,7 suggesting that population-level increases may be due to a higher proportion of fulmars following vessels rather than changes at an individual level. Higher encounter rates were correlated with lower time spent foraging and a geographically restricted overwintering distribution, suggesting an energetic advantage for these scavenging strategists compared with foraging for natural prey.

Evaluation of meso- and microplastic ingestion by the northern fulmar through a non-lethal sampling method.

An increasing number of organisms from the polar regions are reported contaminated by plastic. Rarely a non-killing sampling method is used. In this study we wanted to assess plastic levels using stomach flushing and evaluate the method suitability for further research and monitoring. The stomach of 22 fulmars from Bjørnøya, Svalbard, were flushed with water in the field. On return to the laboratory, the regurgitated content was digested using potassium hydroxide. The extracted plastics were visually characterised and analysed with spectroscopy. Only three birds had plastics in their stomach, totaling 36 particles, most of them microplastics (< 5 mm). The plastic burdens are much lower than previously reported in Svalbard. The stomach flushing is assumed not to allow the collection of the gizzard content. This is a major limitation as most of the plastics accumulate in the fulmar's gizzard. However, the method is still useful for studies investigating plastic ingestion dynamics, allowing to sample the same individuals over time.

Hybridization of Atlantic puffins in the Arctic coincides with 20th-century climate change.

The Arctic is experiencing the fastest rates of global warming, leading to shifts in the distribution of its biota and increasing the potential for hybridization. However, genomic evidence of recent hybridization events in the Arctic remains unexpectedly rare. Here, we use whole-genome sequencing of contemporary and 122-year-old historical specimens to investigate the origin of an Arctic hybrid population of Atlantic puffins (Fratercula arctica) on Bjørnøya, Norway. We show that the hybridization between the High Arctic, large-bodied subspecies F. a. naumanni and the temperate, smaller-sized subspecies F. a. arctica began as recently as six generations ago due to an unexpected southward range expansion of F. a. naumanni. Moreover, we find a significant temporal loss of genetic diversity across Arctic and temperate puffin populations. Our observations provide compelling genomic evidence of the impacts of recent distributional shifts and loss of diversity in Arctic communities during the 20th century.