L.A. Thiele S.C. Garland N.B. Vyas 1998 <p>Effects of a single dietary exposure to fenthion and carbofuran on the survival, feeding behavior and brain ChE activity of eastern screech-owls, <i>Otus asio</i> and American kestrels, <i>Falco sparverius</i>, were evaluated. Birds were exposed to fenthion (23.6–189.0 ppm) or carbofuran (31.7–253.6 ppm) via meatballs. Carbofuran-exposed owls ate either ≤10% or ≥80% of the meatball whereas all kestrels ate ≤10% of the meatball before exhibiting acute signs of toxicity. Fenthion-exposed owls and kestrels displayed a wide spectrum of meatball consumption (&lt;10–100%). Significant brain ChE inhibition was observed in dead and surviving kestrels exposed to fenthion and carbofuran and dead owls exposed to fenthion (<i>P</i>&lt;0.0001). Brain ChE activity of owls exposed to carbofuran that survived was not different from that of controls (<i>P</i>=0.25). Data suggest: (1) slow feeding on a carbamate-contaminated item may provide limited protection from the toxicity of the chemical at certain rates of exposure; (2) the degree of ChE inhibition at neuromuscular junctions may be critical in determining the sensitivity of a species to a carbamate insecticide; (3) sensitivity may be a function of the ChE affinity for the carbamate inhibitor; and (4) the importance of neuromuscular junction ChE depression in determining the sensitivity of an animal may be species-specific.</p> application/pdf 10.1016/S0742-8413(98)00036-X en Elsevier Possible mechanisms for sensitivity to organophosphorus and carbamate insecticides in eastern screech-owls and American kestrels article