Low acute exposure to organophosphate produces long-term changes in bird feeding behavior

Although organophosphates and carbamates are the most widely applied insecticides and are associated with mass killing of birds, little is known of their sublethal effects. One well-known result of sublethal exposure to toxin, conditioned taste aversion, was tested in a series of field experiments in which independent replicates were large numbers of breeding territories of Red-winged Blackbirds (Agelaius phoeniceus). While birds freely consumed untreated insect prey offered to them in control territories, those in treated territories consumed up to three meals of prey tainted with parathion and then utterly avoided these prey during a lengthy posttest when parathion was no longer present. Long-term change in feeding behavior was produced by organophosphate insufficient to induce outward illness or to depress brain AChE activity. The effect was long-term because, unlike noxious repellency, conditioned taste aversion induced by hidden toxin denied birds the opportunity to discriminate between tainted and untainted prey. Although birds may be spared repeated exposure to toxin, continued avoidance of untainted prey disrupts foraging, endangers breeding efficiency, and reduces predation upon pest insects.