Organochlorine chemical residues in white pelicans and western grebes from the Klamath Basin, California

Organochlorine chemical residue levels were assessed in white pelican eggs collected in 1969 and 1981, western grebe eggs collected in 1981, adult pelicans found dead from 1975-1981, and fish collected in 1981. In American white pelican (Pelecanus erythrorhynchos) eggs collected at the Klamath Basin National Wildlife Refuges, concentrations of DDT, DDD and dieldrin declined from 1969 to 1981. DDE and PCB residues from 1969 and 1981 were not significantly different. Between-colony differences in PCB concentrations in 1969 suggested that different pelican colonies wintered in or migrated through different areas. PCB:DDE ratios for white pelican and western grebe (Aechomophorus occidentalis) were 0.13 and 1.58 respectively, suggesting different exposure patterns. Between 1969 and 1981, white pelican eggshell thickness increased, but was less than pre-1947 values. Differences in western grebe shell thicknesses were not significant. Endrin poisoning was the probable cause of death of a considerable proportion of adult pelicans found dead in the Klamath basin from 1975 to 1981. No organochlorine chemical residues were detected in gill-netted fish or in pelican regurgitations. There are 39 references.