Lethal predator control on UK moorland is associated with high breeding success of curlew, a globally near-threatened wader

Abstract

The UK supports a quarter of Eurasian curlew Numenius arquata, so a recent halving of numbers has impacted the global population. Low breeding success is a frequently cited cause of decline. We considered breeding success in relation to predator indices and habitat measures within 18 moorland-farmland blocks across several UK regions. Each block comprised one site where gamekeepers lethally controlled predators on moors managed for red grouse Lagopus lagopus scotica (grouse moor) and another on similar habitat where predators were not controlled (non-grouse moor). More wader species occurred on grouse moors, which supported twice the density of waders as non-grouse moors. Curlew productivity was fourfold higher on grouse moors (1.05 fledglings pair-1) than non-grouse moors (0.27). Hatching and fledging success was negatively linked to a combined index of corvids and fox, which were three- to fourfold fewer on grouse moors but were unrelated to 11 habitats and two livestock grazing variables. Similar patterns were observed in three of four other wader species. These behaviour-based findings were validated by observations on actual nests and broods. Grouse moors appear to act as source populations, thereby slowing the current rapid decline. To halt declines and promote curlew recovery in the UK uplands, we recommend that predator control on grouse moors is maintained and longer term land use policies are developed to render landscapes less friendly to currently high levels of generalist predators.