Barn owls across Europe and North America accumulate lethal rodenticide residues from eating poisoned prey, causing silent population declines.
Anticoagulant rodenticide poisoning causes a slow, distressing death through internal bleeding, weakness and respiratory failure over days to weeks. Because affected owls may appear outwardly normal until near death, the welfare impact is largely invisible. The cumulative burden on populations is significant even when individual deaths are not observed.