High Exposure Rates of Anticoagulant Rodenticides in Predatory Bird Species in Intensively Managed Landscapes in Denmark

  • Thomas Kjær Christensen
  • Pia Lassen
  • Morten Elmeros


The extensive use of anticoagulant rodenticides (ARs) for rodent control has led to widespread secondary exposure in nontarget predatory wildlife species. We investigated exposure rates and concentrations of five ARs in liver samples from five raptors and six owls from Denmark. A total of 430 birds were analysed. ARs were detected in 84–100 % of individual birds within each species. Multiple AR exposure was detected in 73 % of all birds. Average number of substances detected in individual birds was 2.2 with no differences between owls and raptors. Difenacoum, bromadiolone, and brodifacoum were the most prevalent substances and occurred in the highest concentrations. Second-generation ARs made up 96 % of the summed AR burden. Among the six core species (sample size >30), summed AR concentrations were lower in rough-legged buzzard (Buteo lagopus) and long-eared owl (Asio otus) than in barn owl (Tyto alba), buzzard (B. buteo), kestrel (Falco tinnunculus), and tawny owl (Strix aluco). There was a strong tendency for seasonal variations in the summed AR concentration with levels being lowest during autumn, which is probably related to an influx of less-exposed migrating birds from northern Scandinavia during autumn. High hepatic AR residue concentrations (>100 ng/g wet weight), which have been associated with symptoms of rodenticide poisoning and increased mortality, were recorded high frequencies (12.9–37.4 %) in five of the six core species. The results suggest that the present use of ARs in Denmark, at least locally, may have adverse effects on reproduction and, ultimately, population status in some raptors and owls.


Predatory Bird Brodifacoum Anticoagulant Rodenticide Bromadiolone Bird Strike 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank the private taxidermists, the Danish National Veterinary Institute, Copenhagen Airport, natural history museums, and the Danish Society for Animal Welfare for collecting carcasses and tissue samples for the study. Karin R. Petersen and Jeanette Rasmussen are acknowledged for the chemical analyses. Anonymous reviewers are acknowledged for their valuable comments to an earlier draft of the manuscript. The study was financed by the Danish National Forest and Nature Agency.


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Copyright information

© Springer Science+Business Media, LLC 2012

Authors and Affiliations

  • Thomas Kjær Christensen
    • 1
  • Pia Lassen
    • 2
  • Morten Elmeros
    • 1
  1. 1.Department of BioscienceAarhus UniversityRøndeDenmark
  2. 2.Department of Environmental ScienceAarhus UniversityRoskildeDenmark

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