This study examined the exposure of the Eastern Screech-owl (Otus asio) to contaminants in apple orchards of southern Quebec. Using a worstcase scenario approach, secondary exposure to three organophosphorus insecticides, (phosmet, azinphosmethyl and phosalone), two anticoagulant rodenticides, (chlorophacinone and diphacinone), and residues of previously applied organochlorines, particularly DDT and metabolites, was assessed. Exposure to PCBs and trace metals was also considered. Small mammal species preyed upon by Screech-owls were captured in orchards for residue analysis on a continual basis for persistent compounds or after insecticide and rodenticide applications. Beginning in the winter of 2000, 98 nest boxes were constructed and installed in woods inhabited by Screech-owls, adjacent to orchards. These boxes were then repeatedly inspected for pellets and prey remains. Estimated exposure of Screech-owls 0-60 hr post-application was 0.641 mg/kg for phosmet and azinphosmethyl and 0.401 mg/kg for phosalone. Exposure to phosmet at this level may warrant concern. The acute poison zinc phosphide is now the primary means of small mammal control in the study area and the possibility of exposure to anticoagulant rodenticides is diminishing. Observed DDE residues were most elevated in the short-tailed shrew (Blarina brevicauda) and ranged from <1.00 to 26.29 ug/g (wet wt) in whole-body pools. A Screech-owl egg found in a nest box between two orchards may have been thinned by as much as 19.8%, of concern because thinning maintained at 15.0 - 20.0% has been linked to population decline. Only background levels of PCBs and trace metals were detected. Finally, over 950 Screech-owl case files were also obtained from one Canadian and seven United States wildlife rehabilitation facilities and analyzed for evidence that pesticide exposure was an underlying or contributing cause of admissions.

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