Barn owls are acutely vulnerable to secondary rodenticide poisoning when they eat poisoned prey animals. Understanding this threat enables landowners and pest controllers to make more wildlife-friendly choices.
Secondary rodenticide poisoning causes prolonged and painful death in barn owls. The anticoagulant compounds disrupt blood clotting, causing haemorrhage into body cavities and under the skin. Affected birds show weakness, inability to fly and disorientation before dying over a period of days. The sublethal effects of lower-level exposure include impaired coordination, reduced hunting ability and reduced reproductive success. Because barn owls are specialist predators of small mammals and cannot switch prey when rodenticide-contaminated voles are abundant, they are particularly vulnerable to this toxicological pathway.