Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Funding Information: We thank all the fieldworkers for their hard work collecting data. Funding for this study was provided by the Norwegian Ministry for Climate and the Environment, the Norwegian Ministry of Foreign Affairs and the Norwegian Oil and Gas Association along with 8 oil companies through the SEATRACK project (www. seapop. no/ en/ seatrack). Fieldwork in Norwegian colonies (incl. Svalbard and Jan Mayen) was supported by the SEAPOP program (www.seapop.no, grant no. 192141). The French Polar Institute (IPEV project 330 to O.C.) supported field operation for Kongsfjord kittiwakes. The work on the Isle of May was also supported by the Natural Environment Research Council (Award NE/R016429/1 as part of the UK-SCaPE programme delivering National Capability). We thank Maria Bogdanova for field support and data processing. Finally, we thank 3 anonymous reviewers for their help improving the first version of the manuscript.Peer reviewedPublisher PD

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

Inter-population synchrony in adult survival and effects of climate and extreme weather in non-breeding areas of Atlantic puffins

Seabirds are undergoing drastic declines globally and spend the non-breeding season at sea, making it challenging to study the drivers of their survival. Harsh weather and changes in climate conditions can have drastic impacts on seabird population dynamics through increased mortality. The intensity and persistence of extreme events are forecasted to increase with global warming. As shared conditions can induce population synchrony, multi-population studies of key demographic parameters are imperative to explore the influence of climate change. We used long-term mark-recapture data and position (GLS) data to determine non-breeding stop-over areas of five Atlantic puffin (Fratercula arctica) populations over a latitudinal gradient in the north-eastern Atlantic (56°11’–70°23’N). We investigated synchrony in adult survival in relation to shared stop-over areas. We quantified effects of extreme extra-tropical cyclones (ETC) specific to populations’ stop-over areas and the North Atlantic Oscillation on adult survival. Populations with overlapping stop-over areas exhibited temporal synchrony in survival rates. Winter ETCs negatively influenced survival in one population, which was the one most exposed to extreme weather, but did not directly influence adult survival in the other four populations. Synchrony among populations with shared stop-over areas highlights the importance of these areas for adult survival, a key life-history rate. However, extreme weather was not identified as a driving factor for four of the population. This suggests other factors in these areas, likely related to bottom-up trophic interactions, as environmental drivers of synchrony in the survival of Atlantic puffins

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

The occurrence of reindeer calves in the diet of nesting Golden Eagles in Finnmark, northern Norway

To assess the importance of semi-domesticated reindeer Rangifer tarandus calves in the diet of Golden Eagles Aquila chrysaetos, in Finnmark (northern Norway), we collected prey remains at 37 nests over six years (2001-2006). The study area was divided into 1) a fjord area, which is an important calving area for reindeer, and 2) an inland area where few reindeer give birth. 469 prey items were collected over the years. The diet of eagles was numerically dominated by birds (73% of collected prey items), especially willow/rock ptarmigan Lagopus spp. (51%), while mammals made up 27%, with mountain hare Lepus timidus as the most common species. Remains of reindeer calves were found in half of the nests studied and made up 8.5% of the collected prey items: 13.2% in the fjord area and 6.5% in the inland area. There was a higher chance of finding reindeer calves at nests in the fjord area than inland, and in nests situated in birch forest than in pine forest. The number of reindeer calves in the Golden Eagle diet in Finnmark corroborates well other studies from northern Fermoscandia. The importance of the Golden Eagle as a predator on reindeer can't, however, be assessed here

Inter-annual variation in winter distribution affects individual seabird contamination with mercury

International audienceMigratory seabirds are exposed to various pollutants throughout their annual cycle. Among them, mercury (Hg) is of particular concern given its large impact on animal health. Recent studies suggest that winter is a critical period for seabirds when contamination by Hg can be higher than at other times of year. However, individuals within and between species can have different migration strategies that could affect their exposure. Here, we combined multi-year individual tracking data and Hg measurements from 6 Arctic seabird species. We investigated whether inter-annual variations in individual winter contamination with Hg was related to seabird fidelity to a wintering site over years. First, our results show that Hg concentrations above the toxicity threshold (i.e. 5 μg g–1 dry weight in feathers) were observed in variable proportions according to species (from 2% of northern fulmars to 37% of Brünnich’s guillemots). Second, individuals with high fidelity to a wintering ground had more similar Hg concentrations among years compared to individuals with low fidelity, suggesting an effect of their migratory strategy on Hg contamination. Further, we found that the directional change in wintering areas among years influenced seabird Hg contamination, highlighting an additional effect of seabirds’ winter distribution. More specifically, individuals migrating to the northwest direction of a previous wintering ground tended to be more contaminated compared those moving to eastern directions. These results confirm spatial differences in Hg concentration throughout the North Atlantic–Arctic and an east-west gradient increase in Hg concentrations. Verifying this trend will require more large-scale ecotoxicological studies at smaller spatial resolution

Individual migration strategy fidelity but no habitat specialization in two congeneric seabirds

Aim: In migratory species, individuals often use fixed and individual‐specific migration strategies, which we term individual migration strategy fidelity (IMSF). Our goal was to test if guillemots have flexible or fixed individual migration strategies (i.e. IMSF), if this behaviour is consistent across large parts of the genus’ range and if they were philopatric to geographical sites or a habitat feature. Location: North Atlantic. Taxon: Uria spp. Methods: We quantified consistent individual differences in inter‐annual spatial distribution and habitat occupied throughout the non‐breeding period using a large geolocator tracking dataset of 729 adult seabirds breeding at 13 colonies across the Northeast Atlantic and repeatedly tracked up to 7 years over a 9‐year period. Additionally, we used a similarity index to calculate relative fidelity to either geographical sites or habitats and linear mixed‐effects models to assess persistence of spatial site fidelity over multiple years. Results: Both guillemot species exhibited IMSF across a large part of the genus’ range which persisted over multiple years. Individuals of both species and almost all colonies showed fidelity to geographical sites and not to specific habitats. Main conclusions: Guillemots show IMSF that is best explained by site familiarity (fidelity to specific sites) rather than habitat specialization (fidelity to specific habitats). In the context of rapidly changing environments, favourable habitats may permanently shift locations and hence species displaying IMSF driven by site familiarity—such as the genus Uria—may not be able to adjust their migration strategies sufficiently fast to sustain individual fitness and ensure population persistence