Climate-driven ocean warming is profoundly reshaping marine ecosystems, with cascading effects on biodiversity and trophic interactions. For migratory marine predators such as seabirds, demographic responses to warming depend on when and where populations are exposed across the annual cycle. Therefore, integrating demographic monitoring and tracking data, across broad geographic and temporal scales, is essential, given the spatial and seasonal variability in ocean warming. Here, we integrated long-term demographic data, seasonal distributions, and sea surface temperatures (SSTs) for 26 populations of five seabird species breeding in the North-East Atlantic to assess the effects of SSTs on reproduction, survival, and population growth trajectories. Demographic responses varied widely among populations and seasons, but negative effects were most consistently associated with warming during the autumn period postbreeding, particularly in the Barents and East Greenland Seas. Winter warming also corresponded to reduced survival, while breeding-season SSTs showed fewer significant effects on reproductive rates. Populations with dual responses to warming in both the breeding and nonbreeding seasons had the lowest projected population growth rates under future SSTs given a high emissions scenario. These results demonstrate that population vulnerability reflects the interaction between seabirds' year-round distributions and regional ocean warming. This underlines the need to integrate year-round tracking and long-term monitoring to inform conservation strategies and marine spatial planning to ensure climate-resilient marine ecosystems.

Sea ice, a central component of polar ecosystems, is undergoing profound changes due to climate change. In particular, the Arctic is experiencing unprecedented warming at quicker rates than other regions. This alarming trend of sea ice loss has dire consequences, with spill-over effects on the entire ecosystem, from phytoplankton to top predators. The complex and dynamic nature of sea ice gives rise to diverse habitats, each with the potential to affect larger ecosystems in different ways. However, our understanding of the relative importance of different ice types for higher trophic levels remains limited. To address this knowledge gap, we conducted a comprehensive study of the effects of drift ice, landfast ice, and total sea ice extent (landfast ice + drift ice) on the body condition of six species of polar-breeding seabirds using long-term monitoring data (2003-2021) from Kongsfjorden, Svalbard. These species fell into two categories: Arctic species (Little Auk Alle alle, Brünnich’s Guillemot Uria lomvia, and Glaucous Gull Larus hyperboreus) and “boreal” (or north temperate) species (Black-legged Kittiwake Rissa tridactyla, Arctic Skua Stercorarius parasiticus, and Great Skua Stercorarius skua). We found that the presence and extent of different types of sea ice may have different effects on seabird body condition. Though we did not find any relationship between total sea-ice extent and seabird body condition, drift ice and landfast ice extent did produce significant effects. For Arctic species, these effects were positive. For boreal species, the relationship between body condition and drift and landfast ice was more complex. Our study suggests that the use of a non-specific sea ice variable may mask the effects of sea ice on Arctic wildlife, highlighting the importance of not considering sea ice to be uniform and simple habitat.

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.

Understanding spatiotemporal variation in vital rates and population growth rates is a central aim of population ecology, and is critical to conservation of migratory species where different populations may spend the non-breeding season in sometimes widely separated areas. However, estimating those parameters and identifying the underlying drivers of variation for species migrating to remote areas is challenging. The thick-billed murre Uria lomvia is a colonial seabird with a pan-Arctic distribution. Previous studies have documented large-scale spatial variation in population growth in the species’ Atlantic range, with eastern populations declining and western populations being stable, and suggested that this variation was linked to conditions in the wintering areas. We analyse variation in breeding success and adult survival from colonies throughout the Atlantic range, construct region-specific stochastic population models, and compare model predictions to observed colony growth rates. Breeding success was uniformly high in Greenland and Iceland, lower and more variable in Spitsbergen, Bjørnøya and Hudson Bay, and low at Jan Mayen. Adult survival was average or high in all colonies during the 2010s. Observed colony growth rates were lower than modelled growth rates for most populations. This suggests that pre-breeding survival or breeding propensity must have been lower than assumed in many of these populations. Low pre-breeding survival could be linked to poor feeding conditions in fall and winter, possibly influenced by large-scale oceanographic variation. Our results support the idea that seabird populations not subject to breeder mortality due to anthropogenic causes are regulated mainly through variation in pre-breeding survival.

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.

Seabird-fishery interactions are a common phenomenon of conservation concern. Here, we highlight how light-level geolocators provide promising opportunities to study these interactions. By examining raw light data, it is possible to detect encounters with artificial lights at night, while conductivity data give insight on seabird behaviour during encounters. We used geolocator data from 336 northern fulmars Fulmarus glacialis tracked from 12 colonies in the North-East Atlantic and Barents Sea during the non-breeding season to (1) confirm that detections of artificial lights correspond to encounters with fishing vessels by comparing overlap between fishing effort and both the position of detections and the activity of birds during encounters, (2) assess spatial differences in the number of encounters among wintering areas and (3) test whether some individuals forage around fishing vessels more often than others. Most (88.1%) of the tracks encountered artificial light at least once, with 9.5 ± 0.4 (SE) detections on average per 6 mo non-breeding season. Encounters occurred more frequently where fishing effort was high, and birds from some colonies had higher probabilities of encountering lights at night. During encounters, fulmars spent more time foraging and less time resting, strongly suggesting that artificial lights reflect the activity of birds around fishing vessels. Inter-individual variability in the probability of encountering light was high (range: 0-68 encounters per 6 mo non-breeding season), meaning that some individuals were more often associated with fishing vessels than others, independently of their colony of origin. Our study highlights the potential of geolocators to study seabird-fishery interactions at a large scale and a low cost.

The tick species Ixodes uriae, parasitizing seabirds in the Arctic, may transmit many pathogens including various arboviruses, Borrelia spirochetes and Babesia apicomplexans. These pathogens may pose an important additional stress to seabirds, which are already stressed by environmental changes such as pollutants and decreased food availability. Here, we present the results of the first screening for arboviruses of the genera Flavivirus, Alphavirus, Orthobunyavirus, Phlebovirus and Orbivirus, as well as Borrelia spirochetes and Babesia apicomplexans from Svalbard and Jan Mayen. Using polymerase chain reaction technology with genus-specific primers, we tested 89 ticks collected on Jan Mayen, Bjørnøya and Spitsbergen between 2008 and 2012. We did not detect any of the screened tick-borne pathogens. Nevertheless, these pathogens may be introduced to Svalbard and Jan Mayen by migratory birds in the near future. The increasing numbers of ticks appearing in the studied areas make this introduction even more likely. Such an introduction would have serious impact on seabird ecology as well as on human public health. Therefore, continuous careful surveillance and monitoring of possible tick-borne pathogen introductions is important.

Breeding success in cliff-nesting seabirds has until now been estimated through repeated nest checks by field workers during the breeding season. The use of automatic cameras offers a method for collecting mark–recapture data that can be modelled in order to estimate productivity without making recurring inspections. This saves expense and work hours in the field and allows for more colonies to be monitored. Capture histories for Brünnich’s Guillemot Uria lomvia breeding sites in a colony on Svalbard were generated using a series of photos taken by a time-lapse camera during the breeding season. To account for state uncertainty for the offspring when only the adult could be observed on the breeding site, we applied a multievent model. We estimated egg survival, hatching success and chick survival rates by modelling state transitions. Subsequently, the estimates were used to calculate breeding success. In order to assess the performance of the model, we compared the estimates with field observations of productivity. The observed breeding success in the study plot lay within the confidence intervals of the breeding success estimated by our model. We show that automatic cameras can be used to collect data which, by the application of new modelling techniques, will provide reliable estimates of demographic parameters that are vital for research and management of cliff-nesting birds. The method presented is a very good supplement to physical examination or “manual” around-the-clock monitoring of breeding birds.

The parasitic tick Ixodes uriae was recorded from Brünnich's guillemots (Uria lomvia) at two colonies on Spitsbergen, the principal island in the Arctic archipelago of Svalbard. Six Brünnich's guillemots from 30 studied at the Ossian Sars seabird colony were found to be parasitized. A tick was also collected from below the larger Fuglehuken colony. However, ticks were not seen on Brünnich's guillemots examined at the smaller Krossfjorden colony, and neither were they observed in two black-legged kittiwake (Rissa tridactyla) colonies (Blomstrandhalvøya and Krykkjefjellet). It is suggested that either the tick has only recently been established in Svalbard or the population has increased from a low level, and has consequently become visible to small-scale sampling studies. Implications for the seabird population of the northern Barents Sea are discussed.