Shells of brown pelican (Pelecanus occidentalis) eggs collected in South Carolina from 1969 through 1973 were significantly thinner than shells of those collected before 1947. Residues of 10 organochlorine pollutants and 10 heavy metals were found in these eggs. Total organochlorine residues were apparently magnified 23 times from fish to pelican eggs, but interpretation of biomagnification was complicated by the migratory habits of both the pelicans and their chief prey fish. Residues of organochlorine pollutants and heavy metals were also found in tissues of brown pelicans. Dieldrin was probably involved in the death of a pelican that exhibited myocardial necrosis. Other pelicans died from gunshot wounds, various diseases, or unknown causes. From 1969 through 1973, there was a significant decline in residues of p-p'-DDE, p-p'-TDE, p-p'DDT, and dieldrin in eggs of the brown pelican in South Carolina, but the rate of decline was different for each pollutant. PCB's peaked in 1972 and then declined in 1973 to the lowest level in 5 years. In 1973, the first time in many years, South Carolina brown pelicans reproduced very well. The excellent reproductivity seemed related to lowered organochlorine residues and favorable tides, weather, and food supply.
