Bioaccumulation of organochlorine pesticides in the Western Sandpiper (Calidris mauri) during the wintering season in Sinaloa, Mexico

The Western Sandpiper, Calidris mauri, is one of the most abundant migratory shorebirds in the Western Hemisphere. Both Bahia Santa Maria (SM) and Ensenada Pabellones (EP) in Sinaloa, Mexico, are critical wintering sites for this species. We described the presence and concentration of 16 organochlorine pesticides (OCPs) in Western Sandpiper muscle and liver tissues collected from SM and EP during the wintering (December-January) and premigration (March-April) periods of 2010 and 2011, respectively. The individual OCP concentrations varied from 0.003 to 0.127 mu g/g dry weight (dw) and were lower than the established thresholds for either acute or chronic effects. Western Sandpipers in SM-Premigration had the highest frequency of OCPs (39.3%), followed by EP-Winter (32.1%) and SM-Winter (28.5%). The frequency of occurrence of all OCPs in the liver presented differences between sites during the wintering period as well as between the wintering and premigration periods in SM. As the primary organ responsible for pollutant detoxification, the liver may bioaccumulate these compounds. No clear trends were observed in muscle tissues or among age-sex groups. Our results showed evidence of OCP bioaccumulation in the Western Sandpiper during the wintering period, which may be related to hyperphagia during the premigration period and to the differential intake of OCP types and quantities between sites due to differences in their availability. However, these conclusions are based on relatively low sample sizes for some groups and require further study with non-pooled samples.