It may take just a scent, while passing by a restaurant, to jog a memory of a meal gone bad. Many people, after eating something that makes them ill, refuse to consume that food again.
Some birds apparently feel the same way about eating insects that have been exposed to insecticides.
Parathion is an organophosphate, one of the most widely used classes of insecticide in both industrialized and developing nations. The birds were exposed to extremely low levels of parathion, levels too low to induce obvious illness. This suggests the possibility of a widespread, undetected exposure to these insecticides and a loss of important food sources for birds and their nestlings. All the work in this study was done among free-ranging birds, which allowed the researchers to avoid many of the artificialities of captive studies. This was possible because birds in the study were in separate breeding territories.