Organochlorine Pollutants and Stable Isotopes in Resident and Migrant Passerine Birds from Northwest Michoacán, Mexico

compounds (OCs) in birds from most of the United States and Canada have decreased over the last 30 years, there is still concern that migrant birds might be exposed to ele-vated concentrations of OCs during migration in Latin America. The Lerma-Chapala Basin in west-central Mex-ico is an important migration corridor and wintering area for many species. The objectives of this study were to assess if resident and migrant birds wintering in western Michoacán, Mexico accumulated elevated concentrations of OCs during fall and spring and to determine if the stable isotopes d15N, d13C, and dD could be used to predict burdens and origins of DDE accumulation. Resident and migrant passerine insectivorous birds were collected during fall and spring (2001–2002) in northwest Michoacán, near Chapala Lake, Mexico. The carcasses were analyzed fo