Diel rhythms synchronized to Earth's photic cycle are near-ubiquitous among animals living in regions with distinct day-night cues. Where such cues are reduced or absent, however, activity patterns may weaken, reorganize or become decoupled from the light-dark cycle, which may allow for more flexible behavioural expression. Using a dataset of >900 free-ranging black-legged kittiwakes from colonies spanning a broad latitudinal gradient (40-81°N), we show considerable population-level variation in diel activity patterns, from clear 24 h rhythms with distinct peaks at dawn and dusk at lower latitudes, to variable and non-diel rhythms with flattened activity patterns across the 24 h day at high latitudes. These patterns were consistent with the wide spectrum of light-dark cycles experienced across their breeding range, supported by our finding that activity was strongly predicted by sun elevation, suggesting alignment with the light-dark cycle. Together, our findings reveal substantial within-species variation in rhythmicity across latitudes and demonstrate that changes in the photic environment can reshape the temporal organization of activity even within a single, widely distributed species.

Here we investigate the possible link between feeding rates and poor breeding success in an Atlantic puffin (Fratercula arctica) colony on the island Skúvoy in the Faroe Islands. We compare two years of field observations from an early period, 1992 (N = 26) and 1993 (N = 47), with two years of video footage from inside the burrows from 2018 (N = 9) and 2019 (N = 13). 1993 had good breeding success, whereas it was relatively poor in the other three years. Average feedings per day varied between 7.3 (in 1992) and 9.5 (in 2018). Feeding frequency did not differ significantly between early and late years or between good and poorer years. However, the breeding season was shorter in the good year and because of this, chicks were fed fewer times in that year than in the poorer years. Our results suggest the amount or quality of food brought to chicks by parents per feeding event were more important in determining breeding success than number of feedings.

The Faroe Shelf, located on the North Atlantic’s Iceland-Scotland ridge, has historically hosted a rich ecosystem with large seabird populations. However, substantial declines in their population sizes have been observed over the past half century. This study introduces and documents comprehensive decades-long data series from 1972-present on offspring production and adult attendance of four seabird species, the common guillemot, Atlantic puffin, black-legged kittiwake, and Arctic tern, breeding in major colonies in the Faroe Islands. Results show that the highly variable productivity of these seabirds is characterized by marked and synchronized peaks at 5- to 10-years intervals, and these peaks closely mirror indices of primary production and availability of pelagic juvenile fish on the Faroe shelf. These ecological signals are examined in the context of oceanographic changes in the subpolar North Atlantic Ocean, and we argue that the presented seabird series can serve as indicators to enhance the understanding of the Faroe shelf ecosystem and inform the management of both seabird populations and commercial fish stocks.

Demersal fish stocks and seabird populations on the Faroe shelf have declined profoundly over the past half-century, and the relative role of exploitation and climate remains a key question. The dynamics of the subpolar gyre influences both the marine climate and several ecosystems in the northeastern Atlantic. Furthermore, a more than century old hypothesis suggests that production in marine ecosystems along the eastern margin of the Norwegian Sea is fueled by transport of nutrient- and zooplankton-rich subarctic waters from the Iceland Sea-Jan Mayen region. Recent research has, on the other hand, related the productivity of the Faroe shelf ecosystem to local processes. These contrasting perspectives are here combined, to explain the highly variable recruitment, and thus stock sizes, of Faroese cod (Gadus morhua) and guillemots (Uria aalge). We propose that good recruitment to demersal fish stocks and seabirds requires both high on-shelf biological production and high oceanic food content, proxied by large volumes of subarctic waters surrounding the Faroe shelf.

Migration is a common trait among many animals allowing the exploitation of spatiotemporally variable resources. It often implies high energetic costs to cover large distances, for example between breeding and wintering grounds. For flying or swimming animals, the adequate use of winds and currents can help reduce the associated energetic costs. Migratory seabirds are good models because they dwell in habitats characterized by strong winds while undertaking very long migrations. We tested the hypothesis that seabirds migrate through areas with favourable winds. To that end, we used the SEATRACK dataset, a multi‐colony geolocator tracking dataset, for two North Atlantic seabirds with contrasting flight capabilities, the black‐legged kittiwake Rissa tridactyla and the Atlantic puffin Fratercula arctica , and wind data from the ERA5 climate reanalysis model. Both species had on average positive wind support during migration. Their main migratory routes were similar and followed seasonally prevailing winds. The general migratory movement had a loop‐shape at the scale of the North Atlantic, with an autumn route (southward) along the east coast of Greenland, and a spring route (northward) closer to the British Isles. While migrating, both species had higher wind support in spring than in autumn. Kittiwakes migrated farther and benefited from higher wind support than puffins on average. The variation in wind conditions encountered while migrating was linked to the geographical location of the colonies. Generally, northernmost colonies had a better wind support in autumn while the southernmost colonies had a better wind support in spring, with some exceptions. Our study helps understanding how the physical environment shapes animal migration, which is crucial to further predict how migrants will be impacted by ongoing environmental changes.

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 SeabirdMonitoring 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.

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.

Procellariiform seabirds can accumulate high levels of plastic in their gastrointestinal tracts, which can cause physical damage and potentially provides a contamination route for trace elements. We examined plastic ingestion and trace element contamination of fledgling Manx shearwaters Puffinus puffinus that were harvested for human consumption in 2003 and 2018 on Skúvoy, Faroe Islands (North Atlantic Ocean). Overall, 88% of fledglings contained plastic in their gastrointestinal tracts, with a mean (± SD) of 7.2 ± 6.6 items weighing 0.007 ± 0.016 g. Though the incidence was similar, fledglings ingested significantly more plastic in 2018 compared to 2003. Hepatic trace element concentrations were unrelated to plastic ingestion. Hepatic carbon (δ13C) and nitrogen (δ15N) stable isotope values were significantly lower in birds sampled in 2018 versus 2003, potentially reflecting further offshore feeding at lower trophic levels. Future research is needed to understand the extent of plastic ingestion by Faroe Islands seabirds.

Seabird bycatch is common in longline fisheries and detrimental to some seabird populations. Simultaneously, the loss of longline bait to seabirds may pose a considerable economic loss to fishermen. Here, we study northern fulmars (Fulmarus glacialis), bycaught in longline fisheries close to the Faroe Islands between 2004 and 2021. Biological data on age and sex and the quantity of bait in the stomachs was assessed. Males were over-represented in the bycatch sample, as were adult birds, likely caused by sex- and age-specific foraging segregation. Overall, 71% of 820 fulmars contained bait, on average 2 items per bird (range: 0-17 items). No difference in the average number of bait items was detected between males and females or between adult and non-adult birds. During the breeding season, however, adults contained significantly more bait in their stomach than outside the breeding season. No such effect was found for non-adult birds. Together with a lower body condition during the breeding season, this may indicate higher food requirements by breeding birds, potentially increasing entanglement risks. Regular loss of bait reduces fishing efficiency, likely resulting in economic loss. Reducing seabird bycatch may therefore benefit fishermen as well as seabird populations.

During 2021 and 2022 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets Morus bassanus appeared to be especially severely impacted, but a detailed account of the data available is required to help understand how the HPAI virus (HPAIV) spread across the meta-population, and the ensuing demographic consequences. Accordingly, we analyse information on confirmed and suspected HPAIV outbreaks across most North Atlantic Gannet colonies and, for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, and preliminary results on apparent adult survival and serology. Unusually high numbers of dead Gannets were first noted at colonies in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in colonies in Canada and the English Channel. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied nest-sites decreased by at least 71%, breeding success declined by c. 66% compared with the long-term UK mean and the resighting of marked individuals suggested that apparent adult survival between 2021 and 2022 could have been substantially lower than the preceding 10-year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds, indicating that some Gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other challenges faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations as the likelihood of further epizootics increases, due to increasing habitat loss and the industrialization of poultry production.

Since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of mercury (Hg) on Arctic biota in 2011 and 2018, there has been a considerable number of new Arctic bird studies. This review article provides contemporary Hg exposure and potential health risk for 36 Arctic seabird and shorebird species, representing a larger portion of the Arctic than during previous AMAP assessments now also including parts of the Russian Arctic. To assess risk to birds, we used Hg toxicity benchmarks established for blood and converted to egg, liver, and feather tissues. Several Arctic seabird populations showed Hg concentrations that exceeded toxicity benchmarks, with 50 % of individual birds exceeding the "no adverse health effect" level. In particular, 5 % of all studied birds were considered to be at moderate or higher risk to Hg toxicity. However, most seabirds (95 %) were generally at lower risk to Hg toxicity. The highest Hg contamination was observed in seabirds breeding in the western Atlantic and Pacific Oceans. Most Arctic shorebirds exhibited low Hg concentrations, with approximately 45 % of individuals categorized at no risk, 2.5 % at high risk category, and no individual at severe risk. Although the majority Arctic-breeding seabirds and shorebirds appeared at lower risk to Hg toxicity, recent studies have reported deleterious effects of Hg on some pituitary hormones, genotoxicity, and reproductive performance. Adult survival appeared unaffected by Hg exposure, although long-term banding studies incorporating Hg are still limited. Although Hg contamination across the Arctic is considered low for most bird species, Hg in combination with other stressors, including other contaminants, diseases, parasites, and climate change, may still cause adverse effects. Future investigations on the global impact of Hg on Arctic birds should be conducted within a multi-stressor framework. This information helps to address Article 22 (Effectiveness Evaluation) of the Minamata Convention on Mercury as a global pollutant.

The conservation of migratory marine species, including pelagic seabirds, is challenging because their movements span vast distances frequently beyond national jurisdictions. Here, we aim to identify important aggregations of seabirds in the North Atlantic to inform ongoing regional conservation efforts. Using tracking, phenology, and population data, we mapped the abundance and diversity of 21 seabird species. This revealed a major hotspot associated with a discrete area of the subpolar frontal zone, used annually by 2.9–5 million seabirds from ≥56 colonies in the Atlantic: the first time this magnitude of seabird concentrations has been documented in the high seas. The hotspot is temporally stable and amenable to site‐based conservation and is under consideration as a marine protected area by the OSPAR Commission. Protection could help mitigate current and future threats facing species in the area. Overall, our approach provides an exemplar data‐driven pathway for future conservation efforts on the high seas.

This chapter analyses the bird faunas on two Northeast Atlantic island groups, Iceland and the much smaller Faroe Islands. Birds are more mobile than most animal groups. The first Icelandic bird list stems from around 1590 and only mentions about 30 species. The details whereby island communities evolve are subject to general principles of island biogeography; islands generally have fewer species, less competition and greater predation rates. With fossil records hardly existing, the dynamic development of the island bird communities is rather speculative. The history of the immigration and colonization is only known during the last centuries and although the islands have been ice-free for thousands of years new bird species are immigrating. Birds that competed with economic interests were previously violently pursued and slaughtered. Many of the variations in colonization and population sizes are believed to be due to climate change.

Tracking data of marine predators are increasingly used in marine spatial management. We developed a spatial data set with estimates of the monthly distribution of 6 pelagic seabird species breeding in the Northeast Atlantic. The data set was based on year-round global location sensor (GLS) tracking data of 2356 adult seabirds from 2006-2019 from a network of seabird colonies, data describing the physical environment and data on seabird population sizes. Tracking and environmental data were combined in monthly species distribution models (SDMs). Cross-validations were used to assess the transferability of models between years and breeding locations. The analyses showed that birds from colonies close to each other (<500 km apart) used the same nonbreeding habitats, while birds from distant colonies (>1000 km) used colony-specific and, in many cases, non-overlapping habitats. Based on these results, the SDM from the nearest model colony was used to predict the distribution of all seabird colonies lying within a species-specific cut-off distance (400-500 km). Uncertainties in the predictions were estimated by cluster bootstrap sampling. The resulting data set consisted of 4692 map layers, each layer predicting the densities of birds from a given species, colony and month across the North Atlantic. This data set represents the annual distribution of 23.5 million adult pelagic seabirds, or 87 % of the Northeast Atlantic breeding population of the study species. We show how the data set can be used in population and spatial management applications, including the detection of population-specific non-breeding habitats and identifying populations influenced by marine protected areas.

Mercury (Hg) is a natural trace element found in high concentrations in top predators, including Arctic seabirds. Most current knowledge about Hg concentrations in Arctic seabirds relates to exposure during the summer breeding period when researchers can easily access seabirds at colonies. However, the few studies focused on winter have shown higher Hg concentrations during the non-breeding period than breeding period in several tissues. Hence, improving knowledge about Hg exposure during the non-breeding period is crucial to understanding the threats and risks encountered by these species year-round. We used feathers of nine migratory alcid species occurring at high latitudes to study bird Hg exposure during both the breeding and non-breeding periods. Overall, Hg concentrations during the non-breeding period were similar to 3 times higher than during the breeding period. In addition, spatial differences were apparent within and between the Atlantic and Pacific regions. While Hg concentrations during the non-breeding period were similar to 9 times and similar to 3 times higher than during the breeding period for the West and East Atlantic respectively, Hg concentrations in the Pacific during the non-breeding period were only similar to 1.7 times higher than during the breeding period. In addition, individual Hg concentrations during the non-breeding period for most of the seabird colonies were above 5 mu g g(-1) dry weight (dw), which is considered to be the threshold at which deleterious effects are observed, suggesting that some breeding populations might be vulnerable to non-breeding Hg exposure. Since wintering area locations, and migration routes may influence seasonal Hg concentrations, it is crucial to improve our knowledge about spatial ecotoxicology to fully understand the risks associated with Hg contamination in Arctic seabirds. Crown Copyright (C) 2020 Published by Elsevier B.V. All rights reserved.

Each winter, the North Atlantic Ocean is the stage for numerous cyclones, the most severe ones leading to seabird mass-mortality events called "winter wrecks.''(1-3) During these, thousands of emaciated seabird carcasses are washed ashore along European and North American coasts. Winter cyclones can therefore shape seabird population dynamics(4,5) by affecting survival rates as well as the body condition of surviving individuals and thus their future reproduction. However, most often the geographic origins of impacted seabirds and the causes of their deaths remain unclear.(6) We performed the first ocean-basin scale assessment of cyclone exposure in a seabird community by coupling winter tracking data for similar to 1,500 individuals of five key North Atlantic seabird species (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia, and Rissa tridactyla) and cyclone locations. We then explored the energetic consequences of different cyclonic conditions using a mechanistic bioenergetics model(7) and tested the hypothesis that cyclones dramatically increase seabird energy requirements. We demonstrated that cyclones of high intensity impacted birds from all studied species and breeding colonies during winter but especially those aggregating in the Labrador Sea, the Davis Strait, the surroundings of Iceland, and the Barents Sea. Our broad-scale analyses suggested that cyclonic conditions do not increase seabird energy requirements, implying that they die because of the unavailability of their prey and/or their inability to feed during cyclones. Our study provides essential information on seabird cyclone exposure in a context of marked cyclone regime changes due to global warming.(8)

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.

Seabirds provide ecosystem services, notably as human food in many Arctic regions, major tourist attractions, as well as being an important link to the Arctic food web and returning nutrients from the oceans to coastal areas. Changes in seabird populations and diversity will affect regional sustainability for Arctic communities and ecosystems. The CBird Expert Network aggregated and reviewed data on the population status and trends of eight seabird Focal Ecosystem Components (FECs) across eight Arctic Marine Areas as well as the state of current monitoring efforts for these species. Population trends for seabirds vary within and among regions, making it difficult to assess circumpolar trends. Nonetheless, among key sites, current trends indicate that most of the stable or increasing populations are in the Pacific Arctic and Arctic Archipelago, while most of the declining populations are in the Atlantic Arctic. Most circumpolar nations have at least one source of long-term seabird monitoring datasets, but efforts vary across regions. Long-term monitoring efforts are crucial to examining the effects of environmental drivers to changes in seabird populations. The presentation will summarize current level of monitoring across the Arctic, the status and trends of FECs, drivers of observed trends, and knowledge and monitoring gaps.

Since the open-ocean subpolar Atlantic is amongst the most predictable regions in the world, our results hold promise for predicting the general production to seabird populations over a large geographical region adjacent to the northern North Atlantic and the Arctic Mediterranean. Colonies of black-legged kittiwakes Rissa tridactyla in the North Atlantic have declined markedly since the mid-1990s, partly due to repeatedly failing breeding seasons. We show a close link between the breeding success of a kittiwake colony in the Faroe Islands and the subpolar gyre index. Successful breeding follows winters with an expanded subpolar gyre and, by inference, increased zooplankton abundances southwest of Iceland. The environmental conditions in the northwestern Atlantic during the non-breeding and pre-breeding seasons might therefore be important. Furthermore, the subpolar gyre dynamics might influence the local food abundance on the Faroe shelf during the breeding season.

Carry-over effects, whereby events in one season have consequences in subsequent seasons, have important demographic implications. Although most studies examine carry-over effects across 2 seasons in single populations, the effects may persist beyond the following season and vary across a species’ range. To assess potential carry-over effects across the annual cycle and among populations, we deployed geolocation loggers on black-legged kittiwakes Rissa tridactyla at 10 colonies in the north-east Atlantic and examined relationships between the timing and destination of migratory movements and breeding success in the year of deployment and subsequent season. Both successful and unsuccessful breeders wintered primarily in the north-west Atlantic. Breeding success affected the timing of migration, whereby unsuccessful breeders departed the colony earlier, arrived at the post-breeding and main wintering areas sooner, and departed later the following spring. However, these patterns were only apparent in colonies in the south-west of the study region. Furthermore, the effect of breeding success was stronger on migration timing in the first part of the winter than later. Timing of migratory movements was weakly linked to subsequent breeding success, and there was no detectable association between breeding success in the 2 seasons. Our results indicate temporal structure and spatial hetero - geneity in the strength of seasonal interactions among kittiwakes breeding in the north-east Atlantic. Variable fitness consequences for individuals from different colonies could have important implications for population processes across the species’ range and suggest that the spatio-temporal dynamics of carry-over effects warrant further study.