Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
Secondary Poisoning of Birds of Prey by Anticholinesterase Insecticides
J.E. Elliott 1,2 , L.K. Wilson 1,2 , K.M. Langelier 2 and P. Mineau 2
1 Canadian Wildlife Service
2 Environment Canada
Abstract
The effects of persistent organochlorine (OC) contaminants, such as DDT and dieldrin, on raptor populations has
been widely documented. OCs have largely been replaced by organophosphorus (OP) and carbamate insecticides
which are considered non-persistent, non-bioaccumulative and therefore, of low risk for secondary poisoning of
raptors. However, we present evidence that granular formulations of OP and carbamate insecticides can persist
long enough in the wet, low pH conditions of the Fraser River delta of British Columbia, to cause waterfowl kills
and secondary poisoning of raptors several months after pesticide application. Various raptors, particularly bald
eagles (Halaeetus leucocephalus) and red-tailed hawks (Buteo jamaicensis), have been obtained, dead or
debilitated, from government and non-government sources. All specimens were analyzed for plasma and/or brain
cholinesterase activity. Based on those results, ingesta were analyzed for pesticide residues.
From 1990 to 1994, mostly in the Fraser delta, more than 40 cases were documented of raptors poisoned by
anticholinesterases. Over a three-year period in the delta, an average of 20% of bald eagles examined (N=157)
were poisoned by anticholinesterases. At least seven insecticides have been implicated, resulting in the
withdrawal of some compounds from the local market.
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