Patterns of organochlorine pesticide contamination in neotropical migrant passerines in relation to diet and winter habitat.

Eleven species of Neotropical migrant passerines collected in Illinois (USA) during May 1996, were analyzed for the presence of organochlorine (OC) pesticides. At least one of five OC pesticide residues was detected in 66 of 72 birds, representing all species examined. The contaminants most frequently detected were p,p'-DDE, dieldrin and heptachlor epoxide, all of which were present in the 10-30 ng/g range. Insectivores had significantly higher levels of these compounds than did non-insectivores, while there was no significant main effect of winter habitat (forest and scrub). Future research on OC pesticide contamination in resident New World passerines may allow more accurate predictions regarding the sources of contamination in Neotropical migrants.