use of stopover sites by Black Storks (Ciconia nigra) migrating between West Europe and West Africa as revealed by satellite telemetry

Migration is known to be a bottleneck in the annual cycle of many birds, and its success can depend on the availability of stopovers along the migration route. Satellite tracking was used to identify migratory strategies and important stopovers in 16 Black Storks (Ciconia nigra) during their autumn and spring migrations between European breeding areas and West African wintering sites. Some birds migrate without using stopovers, whereas others need to stop at least once during their migration: 1-5 stopovers were observed per bird, and half of all stopovers were located in Spain. Precise GPS locations indicated that it is unlikely that the storks forage near their night roost, just after or before their migratory flights. For the birds that do make stopovers, the tracking data reveal both inter- and intra-individual variability in the use of stopovers over the two migrations, suggesting a lack of fidelity to such sites. The number of stopovers was similar for potential breeders and non-breeders, although the length of stopovers was significantly longer for non-breeders than for potential breeders. No difference in stopover duration was found between autumn and spring migrations. Six stopovers were considered as important ones, based on the time spent there (>10 days). This study underlines the importance of protected areas along migratory paths and the necessity to plan protective measures for those stopover sites.