Weather mediated impacts on the breeding output of an Afro-Palearctic migratory waterbird

Understanding the consequences of changing environmental conditions on the demographic parameters of migratory species is key for addressing the widely reported declines for many of these species. We explore the variation in reproductive investment and output of Purple Herons (Ardea purpurea) in two breeding seasons, with very different precipitation levels but similar temperatures. Despite similar investment in egg volume, reproductive output in the drier year was less than half of the wetter year (∼1.9 vs ∼4.1 chicks per pair) due to weather mediated higher predation. The current predictions of erratic precipitation and warming may threaten the breeding output of waterbirds, if water levels are unsuitable during the breeding season.