WA5 Wildlife Toxicology: Forensic Approaches
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() Poisoning of birds of prey by anticholinesterase insecticides in agricultural areas of southwestern British Columbia.

Elliott, J1, Wilson, L 1, Mineau, P2, McAdie, M3, 1 Canadian Wildlife Service, Delta, BC, Canada2 Canadian Wildlife Service, Ottawa, ON, Canada3 British Columbia Ministry of Water, Lands & Parks, Nanaimo, BC, Canada

ABSTRACT- Since 1990, we have investigated mortality of selected raptor species, particularly bald eagles, in southwestern British Columbia. Carcasses and sick birds were obtained from a network of rehabilitators, veterinarians and conservation officers. Samples of blood and crop contents were collected whenever possible from live birds, and all dead birds were necropsied and brains assayed for cholinesterase activity. To date we have examined 780 bald eagles and diagnosed anticholinesterase poisoning in 80 (10.2% of cases). In the Fraser River Delta, an area of both intensive agriculture and raptor wintering, of 183 bald eagles examined, 53 (29%) were poisoned by anticholinesterase insecticides. Most raptor poisonings occurred during winter and resulted from scavenging on waterfowl carcasses. The ducks were poisoned from ingestion of granules of registered organophosphorus (OP) or carbamate insecticides which had been applied the previous spring for control of wireworm. We have shown that some OP and carbamate insecticides persist up to nine months after labeled application in the low pH conditions of the Fraser delta The first documented mortalities in 1990 were caused by carbofuran. Successive replacement of carbofuran (avian HD5= 0.21 mg/kg) with progressively less toxic, but not necessarily less persistent, alternatives, phorate (HD5=0.34 mg/kg) and fonofos (HD5=3.86 mg/kg) failed to stop and in some cases increased annual poisonings of bald eagles and other raptors. Each of those chemicals has since been withdrawn from local use. Since 2000, chlorpyrifos (HD5=3.76 mg/kg), under a year-by-year registration for wireworm control, has not been related to raptor mortality. Increasing numbers of wintering bald eagles overall in the Pacific Northwest, particularly in the Fraser Delta, and increased scavenging of eagles on waterfowl factor into the long term and seasonal trends in poisonings.

Key words: Insecticides, Raptors, Mortality, Cholinesterase

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