Wild Barn Owl Diet and Rodenticide Secondary Poisoning

Barn owls are highly susceptible to secondary poisoning from anticoagulant rodenticides consumed by their prey, and widespread rodenticide use is a significant and preventable cause of barn owl mortality.

Key Facts

Studies of barn owl carcasses in the UK consistently find second-generation anticoagulant rodenticide (SGAR) residues in over 80 percent of individuals
Field voles and wood mice — primary barn owl prey — are not the primary non-target SGAR accumulation species, but rats and house mice that consume bait are eaten by owls
SGARs (brodifacoum, bromadiolone, difethialone) accumulate in prey and in owls, causing haemorrhage and death
The UK Campaign for Responsible Rodenticide Use (CRRU) Code restricts SGAR use to trained operators and requires monitoring
First-generation anticoagulants (chlorophacinone, warfarin) carry lower secondary poisoning risk for birds of prey
Non-rodenticide methods including proofing, trapping, and electromagnetic devices should be first-line pest control

Welfare Considerations

Secondary SGAR poisoning causes a slow, distressing death in barn owls through internal haemorrhage affecting multiple organs. Owls with sub-lethal SGAR exposure may show impaired coordination, reduced hunting success, and susceptibility to trauma — weakened birds are more likely to be hit by vehicles. The persistence of SGARs in the food chain means contamination continues long after baiting operations cease. The high prevalence of SGAR residues in UK barn owls — in areas far from intensive rodenticide use — indicates that diffuse environmental contamination is widespread. Transitioning to first-generation rodenticides, non-chemical pest control, and Rodenticide Stewardship Group compliance reduces the welfare burden on barn owls and other raptors.

What You Can Do

Use first-generation anticoagulant rodenticides (warfarin, coumatetralyl) rather than SGARs when rodenticide use is necessary
Implement proofing, trapping, and exclusion as first-line rodent control before reaching for rodenticides
Ensure any SGAR use follows CRRU Code stewardship requirements — professional use only, with monitoring and bait security
Submit barn owl carcasses found dead to the Environmental Research Group Oxford (ERGO) for residue testing to contribute surveillance data