Chemical and biochemical evaluation of Swainson's hawk mortalities in Argentina
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Several isolated incidents of Swainson's hawk (Buteo swainsoni) mortality were reported in the Pampas regions of Argentina during the austral summer of 1996. Eighteen sites containing 5,093 dead hawks were identified. Four sites, I, II, III, and IV, containing 387, 103, 3024, and 595 hawk mortalities, respectively, were investigated. Landowner and pesticide applicator interviews indicated use of the organophosphate pesticides (OP) monocrotophos at sites I and IV and dimethoate at site II. The agent used at site III was unknown due to conflicting reports. However, brain and plasma cholinesterase activity were sufficiently depressed in the hawks found at site III to indicate exposure to an OP. Brain and plasma acetylcholinesterase (AChE) taken from several dead and incapacitated birds were depressed 90% and 50%. Dimethoate, methamidiphos, methyl parathion, and chlorpyrifos were suspected, but only monocrotophos was found in several gastrointestinal (GI) tracts. No other parent OPs were detected from any of the sites. Dimethylphosphoroate, the primary metabolite of a dimethylphosphate insecticide, was detected in GI tracts from sites I and IV. The absence of dialkylthiophosphates precluded the use of any phosphorothioate or phosphorodithioate insecticide. Based upon these findings, monocrotophos was responsible for the mortalities at sites I, III, and IV, and dimethoate for site II.
author list (cited authors)
Scollon, E. J., Goldstein, M. I., Parker, M. E., Hooper, M. J., Lacher, T. E., & Cobb, G. P.