Organochlorine concentrations, whole body weights, and lipid content of black skimmers wintering in Mexico and in south Texas, 1983

Since 1978, a large proportion of the black skimmers (Rynchops niger) nesting along the Texas coast have had high concentrations of DDE in their eggs. Of 284 eggs collected from 5 sites during 1978-81, 99.5% contained detectable (> 0.i0 ppm) w levels of DDE, ranging up to 86 ppm wet-weight; 36% of the eggs contained > i0 ppm DDE (White et al., 1984). During the 4-year period, geometric mean concentrations of DDE remained strikingly similar, with no significant decline in egg contaminant levels. The sources of DDE contamination in skimmers are unknown. Recoveries of juvenile skimmers banded in Texas, Louisiana, and Mississippi indicate that a large proportion of the birds (60%) spend the winter on the east and west coasts of Mexico. Therefore, it is possible that the DDE exposure to Texas skimmers occurs in Mexico during the winter, although some birds remain along the Gulf Coast year-round.\

This study was conducted to determine the degree of DDE and other organochlorine contamination in black skimmers and their food items from sites in Mexico and Texas, and to statistically compare residue concentrations and body condition in individuals from the 2 areas.