Anticoagulant rodenticides in sparrowhawks: a Predatory Bird Monitoring Scheme (PBMS) report

Walker, L.A.; Chaplow, J.S.; Moeckel, C.; Pereira, M.G.; Potter, E.D.; Shore, R.F.. 2015 Anticoagulant rodenticides in sparrowhawks: a Predatory Bird Monitoring Scheme (PBMS) report. Lancaster, NERC/Centre for Ecology & Hydrology, 12pp. (CEH Project no. C05191)

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The Predatory Bird Monitoring Scheme (PBMS; is the umbrella project that encompasses the Centre for Ecology & Hydrology’s National Capability activities for contaminant monitoring and surveillance work on avian predators. The PBMS aims to detect and quantify current and emerging chemical threats to the environment and in particular to vertebrate wildlife. Second generation anticoagulant rodenticides (SGARs) can be toxic to all mammals and birds. The PBMS together with other studies have shown that in Britain, there is widespread exposure to SGARs in a diverse range of predators of small mammals. Defra’s Wildlife Incident Monitoring Scheme (WIIS) and the PBMS have shown that some mortalities result from this exposure. The main transfer pathway for SGARs has been thought to be most likely via target and non-target rodents that eat SGAR bait. However, recent studies, including a preliminary analysis by the PBMS on sparrowhawks, Accipiter nisus, have suggested that that SGAR transfer through avian transfer pathways may also be important. The aims of the current study were to build on our earlier results by analysing a further 52 sparrowhawks for liver SGAR residues, and using the combined dataset to (i) assess overall levels of exposure in sparrowhawks from across Britain and (ii) determine if age and sex affect the magnitude of liver SGARs residues. A final aim was to compare exposure (assessed from liver residues) in sparrowhawks with that of the barn owl Tyto alba, a predator that takes predominantly small mammals We found one or more SGARs in the livers of 89% of the 94 sparrowhawks we analysed; all birds were collected by the PBMS between 2010 and 2013. A high proportion of these residues were relatively low and none were associated with haemorrhaging unconnected with physical trauma. The proportion of birds with detectable residues and the magnitude of those residues were significantly higher in adults than juveniles, but residues did not vary significantly between males and females. Comparison of liver SGAR residues in barn owls and sparrowhawks that had died over a similar time period indicated that, for both adults and juveniles, sparrowhawks were as likely to have detectable liver SGAR residues as barn owls but the magnitude of the residues was lower in sparrowhawks. Overall this study has demonstrated that food-chain transfer of SGARs can occur via a predominantly avian trophic pathway and lead to secondary exposure.

Item Type: Publication - Report
UKCEH and CEH Sections/Science Areas: Shore
Funders/Sponsors: NERC/Centre for Ecology & Hydrology, Natural England, Royal Society for the Protection of Birds, Defra, Scottish Environment Protection Agency, Scottish Natural Heritage
Additional Keywords: annual report, birds of prey, rodenticide, barn owl, sparrowahwk, difenacoum, bromadiolone, brodifacoum, flocoumafen, difethialone, monitoring, United Kingdom, UK
NORA Subject Terms: Ecology and Environment
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Date made live: 12 Jun 2015 15:58 +0 (UTC)

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