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

Abstract

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 Michoacán, Mexico accumulated elevated concentrations of OCs during fall and spring and to determine if the stable isotopes d 15 N, d 13 C, 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 for OCs and tail feathers were analyzed for stable isotopes d 15 N, d 13 C, and dD. The OCs detected in more than 50% of the samples were: oxychlordane (79%), p,p'-DDE (100%), p,p 0 -DDT (57%), and total PCBs (100%). p,p 0 -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 lg/g wet weight in carcass. There were no significant differences in d 13 C and d 15 N values among species, between seasons, or between migrant and resident birds. However, dD values were clearly different between species and helped differentiate migrant from resident birds. dD values also were negatively and significantly correlated with DDE concentrations in carcass. Birds with more depleted dD values in feathers tended to have higher DDE concentrations than those with less depleted dD 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 Michoacán, Mexico.

Temporal and latitudinal trends of p,p′‐DDE in eggs and carcasses of North American birds from 1980 to 2005

“…Also, other studies have shown that some migratory birds use more nutrients acquired in their breeding grounds for egg production and accumulate more contaminants from the breeding grounds in their eggs . In a recent study, we showed that some passerine migrant birds, which likely nest in northern latitudes in the United States and southern Canada, appeared to have slightly greater DDE residues than passerine resident species from western Michoacán, Mexico . Thus, we assumed that the DDE concentrations observed in carcass and eggs in these reviewed studies reflected local acquisition rather than distant sources.…”

“…It has been hypothesized for many years that North American migrant birds wintering in Latin America acquire contaminants such as DDE in their wintering areas and bring them back to their breeding grounds [27]. However, this hypothesis has been difficult to confirm and has been refuted by various studies [27][28][29][30][31][32][33][34]. Also, other studies have shown that some migratory birds use more nutrients acquired in their breeding grounds for egg production and accumulate more contaminants from the breeding grounds in their eggs [35,36].…”

“…For many years, particularly after the DDT ban in the United States and Canada in the early 1970s, it was hypothesized that migratory birds were acquiring DDT and metabolites while in the wintering grounds in Mexico and Central America [27]. However, the few contaminant studies conducted in the wintering grounds have not shown a clear pattern of DDE accumulation in migrant birds while in Mexico or in their wintering grounds [27][28][29][30][31][32][33][34]. Also, stable isotope studies revealed that migratory birds such as double-crested cormorants (Phalacrocorax auritus), migratory gulls, and terns use more nutrients acquired in the breeding grounds and accumulate more contaminants from the breeding grounds in their eggs [35,36].…”

Estado Actual De La Investigación Sobre Plaguicidas en México

“…De hecho, Mora et al (2011) reportaron la presencia de DDE en huevos de halcón aplomado (Falco femoralis septentrionalis) colectados en áreas de anidación de Chihuahua (7.85 µg/g base lipídica) y Veracruz (5.51 µg/g), aunque el grosor del cascarón no mostró signos de adelgazamiento debido al DDE. Por otro lado, aves paseriformes residentes colectadas en zonas adyacentes al lago de Chapala en Michoacán (Mora 2008), mostraron concentraciones máximas de DDE de hasta 12 µg/g, mientras que aves migratorias presentaron concentraciones de DDE de hasta 0.01 µg/g. Este estudio indicó una posible fuente local (drenaje pluvial) de plaguicidas.…”