Although concentrations of organochlorine 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 elevated concentrations of OCs during migration in Latin America. The Lerma-Chapala Basin in west-central Mexico 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 Michoaca??n, Mexico accumulated elevated concentrations of OCs during fall and spring and to determine if the stable isotopes ??15N, ??13C, and ??D 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 Michoaca??n, near Chapala Lake, Mexico. The carcasses were analyzed for OCs and tail feathers were analyzed for stable isotopes ??15N, ??13C, and ??D. The OCs detected in more than 50% of the samples were: oxychlordane (79%), p,p'-DDE (100%), p,p???-DDT (57%), and total PCBs (100%). p,p???-DDE was the OC detected at the highest concentrations, whereas residues of other OCs were near or below detection limits. Overall, there were no significant differences in concentrations of OCs between seasons or between resident and migrant birds. Concentrations of DDE and oxychlordane were somewhat higher in migrant and resident birds during spring than in fall; however, concentrations were significantly different only for oxychlordane. Two resident birds collected in fall and spring had DDE residues >10 ??g/g wet weight in carcass. There were no significant differences in ??13C and ??15N values among species, between seasons, or between migrant and resident birds. However, ??D values were clearly different between species and helped differentiate migrant from resident birds. ??D values also were negatively and significantly correlated with DDE concentrations in carcass. Birds with more depleted ??D values in feathers tended to have higher DDE concentrations than those with less depleted ??D values, suggesting a potential latitudinal accumulation of DDE. Overall, our results suggest that during fall and spring, there is not a significant buildup of persistent OCs in migrant and resident passerine insectivorous birds in northwest Michoaca??n, Mexico. ?? 2008 Springer Science+Business Media, LLC.
Additional Publication Details
Organochlorine pollutants and stable isotopes in resident and migrant passerine birds from northwest Michoaca??n, Mexico
Archives of Environmental Contamination and Toxicology