Spatially explicit risk mapping reveals direct anthropogenic impacts on migratory birds

Aim Migratory species rely on multiple ranges across the annual cycle, rendering them vulnerable to a wide range of spatially disparate anthropogenic threats. The spatial distribution of these threats will strongly influence the magnitude of their population-scale effects, but this has not been quantitatively assessed for most species. Location Europe, Central Asia, Western Asia, Africa. Time period Modern. Major taxa studied Aves. Methods We combined remote-sensed data and expert opinion to map 16 anthropogenic threats relevant to migratory birds across Europe, Africa and the Middle East - including the first spatially-explicit pan-continental assessment of relative hunting pressure. By combining the resulting composite threat maps with species range polygons and morpho-behavioural traits-based weightings (reflecting relative threat susceptibility), we created species-specific risk maps for 103 Afro-Palaearctic migratory birds breeding in Europe and evaluated how spatial threat vulnerability relates to long-term population trends. Results We found that greater vulnerability to direct mortality threats (including hunting pressure, infrastructure and nocturnal lights), especially in the non-breeding season, is associated with declining bird population trends. Main conclusions Our results emphasize the importance of spatially explicit approaches to quantifying anthropogenic drivers of population declines. Composite risk maps represent a valuable resource for spatial analyses of anthropogenic threats to migratory birds, allowing for targeted conservation actions.