Small Space but High Diversity: Spatial and Temporal Habitat Use by Endangered Eurasian Curlew at Wintering Sites Throughout Europe

Coastal, and to a lesser extend inland wetlands, are critical habitats for wintering shorebirds. Given the significant population declines of most shorebird species worldwide, the current degradation of coastal habitats through climate change and human activities raises severe conservation concerns. In order to ensure sufficient and adequate habitats and maintain the populations, a thorough understanding of space use by wintering shorebirds is urgently required. However, overwintering strategies have rarely been investigated throughout the entire range of a shorebird species. This study thus aimed to investigate the spatio-temporal use of wintering habitats by Eurasian curlew Numenius arquata on a European scale, using a large international dataset. A total of 204 adult curlews were tagged with GPS devices at different wintering and breeding sites across Europe between 2014 and 2021, and the data were used to analyse home range size, habitat use, and phenology. The birds were faithful to their wintering sites throughout the winter. Their home ranges were small compared with other shorebirds but highly variable between individuals (533 ± 449 ha). Winter home range areas did not differ in relation to sex or body mass, but were weakly related to the wintering latitude, particularly linked to the many birds wintering in the Wadden Sea. Curlews used a high diversity of coastal and inland habitats, with higher occurrences on mudflats and saltmarshes. Despite the inter-individual variability in space use, the high wintering-site fidelity shown by this near-threatened species raises concerns about its capacity to respond to environmental modifications in coastal regions.