Early post-release survival and predation in headstarted Eurasian Curlews Numenius arquata

Grassland-breeding waders are highly vulnerable to population declines, primarily due to the combination of agricultural intensification and predation. In Europe, agri-environment schemes (AESs) and site protection have been the main strategies implemented in order to improve breeding success. Additional various actions have also been taken in an effort to improve breeding success. However, despite these efforts, many wader populations continue to decline. Headstarting, which includes the collection of eggs from the wild and the captive raising of chicks prior to release, has been employed to help restore endangered wader species. This study examined the early post-release survival of GPS-tracked headstarted Eurasian Curlews Numenius arquata (n = 62) at several sites in Poland. Overall survival from release to migration was 0.42, with the highest mortality occurring within the first seven days after release. All known mortalities were attributed to predation. Most predation occurred during the day. Mammalian predators were recorded more frequently than avian predators. No effect of year, release site, cohort size, or release date on survival was found. Predation probability was higher in areas with greater total lengths of roads and ditches, and at shorter distances to ditches. The probability of daytime predation was higher near trees, whereas the probability of nocturnal predation was greater near buildings. Predation risk during the early post-release period may be minimised by avoiding release sites with a dense network of roads and ditches, with many scattered trees, or close to farms and rural settlements.