Abstract
Seabirds are particularly vulnerable to the direct and indirect effects of climate change, however little is known about those impacts outside of the breeding season. This lack of knowledge is problematic because the conditions encountered during migration and wintering strongly shape seabird population dynamics. It is therefore essential to understand the effects of climate on their winter distribution and migration routes. Linking the distribution of organisms to environmental factors is therefore a primary task benefiting from the concept of energyscapes (defined as the variation of an organism's energy requirements across space according to environmental conditions) which has recently provided a mechanistic explanation for the distribution of many animals. In this context, we have predicted the current and future winter habitats of five species representing 75% of the seabird community in the North Atlantic (Alle alle, Fratercula arctica, Uria aalge, Uria lomvia and Rissa tridactyla). To this aim, we monitored the movements of more than 1500 individuals to identify the birds' preferred habitats through resource selection functions based on the modeling of their energy expenditure and prey availability. Electronic tracking data were also overlaid with cyclone locations to map areas of high exposure for the seabird community across the North Atlantic. In addition, we explored the energetic consequences of seabird exposure to storms using a mechanistic bioenergetic model (Niche MapperTM). Finally, we examined the impact of total summer sea ice melt from 2050 on Arctic bird migration. Our analyses predict a northward shift in the preferred wintering areas of the North Atlantic seabird community, especially if global warming exceeds 2°C. Our results suggest that cyclonic conditions do not increase the energy requirements of seabirds, implying that they die from the unavailability of prey and/or inability to feed during cyclones. Finally, the melting sea ice at the North Pole may soon allow 29 species of Arctic birds to make new trans-Arctic migrations between the Atlantic and the Pacific. We also estimate that an additional 26 currently migratory species could remain in the Arctic year-round. This work illustrates how climate change could radically alter the biogeography of migratory species and we provide a methodological toolbox to assess and predict these changes by combining movement ecology and energetic physiology.