Anticoagulant Rodenticides in Three Owl Species from Western Canada, 1988–2003

  • Courtney A. Albert
  • Laurie K. Wilson
  • Pierre Mineau
  • Suzanne Trudeau
  • John E. ElliottEmail author


Anticoagulant rodenticides are widely used to control rodent infestations. Previous studies have shown that nontarget organisms, such as birds, are at risk for both primary and secondary poisoning. This paper presents rodenticide residue information on the livers from 164 strigiformes which included barn owls (Tyto alba), barred owls (Strix varia), and great horned owls (Bubo virginianus), collected from 1988 to 2003 in the province of British Columbia and the Yukon Territory, Canada. Livers were analyzed for brodifacoum, bromadiolone, chlorophacinone, diphacinone, difethialone, and warfarin. Our results show that, of the 164 owl livers analyzed, 70% had residues of at least one rodenticide, and of these 41% had more than one rodenticide detected. Of the three species of owls examined, barred owls were most frequently exposed (92%, n = 23); brodifacoum and bromadiolone were most often detected, with liver concentrations ranging from 0.001 to 0.927 mg/kg brodifacoum, and 0.002 to 1.012 mg/kg bromadiolone. Six of the owls (three barred owls, two barn owls, and one great horned owl) were diagnosed as having died from anticoagulant poisoning; all six owls had brodifacoum residues in the liver.


Bait Station Brodifacoum Anticoagulant Rodenticide Bromadiolone Diphacinone 
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We thank the following agencies for submitting owl carcasses to our agency: the British Columbia Ministry of Environment including Karen Morrison in Nanaimo, Jack Evans in Surrey, and Orville Dyer in Penticton as well as all Conservation Officers throughout B.C.; the Yukon Department of Renewable Resources (Bruce Bennett); Orphaned Wildlife Rehabilitation Society (OWL), Monika’s Wildlife Shelter, Wildlife Rescue Association (WRA), North Island Wildlife Recovery Association (NIWRA), Mountainaire Avian Rescue Society (MARS), South Okanagan Rehabilitation Center for Owls (SORCO), and Fur and Feather Taxidermy. Sandi Lee is thanked for her assistance with field studies. National Wildlife Research Centre staff are thanked for specimen bank archiving and rodenticide residue analysis. Thanks are extended to Dr. Malcolm McAdie and Craig Stephens and staff at the Centre for Coastal Health for conducting post mortem examinations. Funding was from the Canadian Wildlife Service and the Pesticide Science Fund of Environment Canada.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Courtney A. Albert
    • 1
  • Laurie K. Wilson
    • 2
  • Pierre Mineau
    • 3
  • Suzanne Trudeau
    • 3
  • John E. Elliott
    • 1
    Email author
  1. 1.Science and Technology BranchEnvironment Canada, Pacific and Yukon RegionDeltaCanada
  2. 2.Canadian Wildlife ServiceEnvironment Canada, Pacific and Yukon RegionDeltaCanada
  3. 3.Science and Technology Branch, Environment CanadaNational Wildlife Research CenterOttawaCanada

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