Nest survival of threatened Eurasian Curlew (Numenius arquata) breeding at low densities across a human-modified landscape

Targeted management actions to boost key demographic rates can help to restore rare and localized populations but are increasingly required to stabilize or reverse declines of formerly common and widespread species. Many breeding wader populations across Europe are declining because of unsustainably low rates of productivity, and the conservation tools designed to boost wader breeding productivity have been most effectively used for semi-colonial species within protected areas. Targeted management for wader species that breed at low densities across human-modified landscapes, such as the rapidly declining Eurasian Curlew Numenius arquata, is likely to be more challenging. Here, we quantify variation in Curlew nest survival to explore how management could be targeted to boost this key component of breeding productivity. Up to 80 pairs of Eurasian Curlew were monitored annually between 2019 and 2021 in eight locations across Breckland, eastern England, where nesting densities range from c 0.7 pairs/km(2). For 136 nests across grassland- and arable-dominated sites, the majority of failures (86%) were caused by (primarily nocturnal) predation and the mean probability of surviving incubation (PSI) for all hatched or predated nests (127) was c. 0.25. Nest survival showed little annual or seasonal variation but did vary slightly between sites; however, this spatial variation was not clearly related to management conditions or nest concealment at these sites. Fencing to exclude mammalian nest predators can be effective for waders, but too few Eurasian Curlews currently nest within fenced areas in Breckland to produce observable effects. Fencing the few sites with high nesting densities could potentially double the number of chicks hatched each year within the study area, but landscape-scale actions to reduce predator impacts on nests and chicks are likely to be needed to maintain breeding numbers in the wider countryside.