Organochlorine and metal residues in royal terns nesting on the central Texas coast

Royal Tern eggs collected from Pelican and Sundown islands on the central Texas coast in 1978 contained relatively low levels of organochlorine and metal pollutants. DDE and PCBs were found most frequently, but levels were below those known to have an adverse effect on avian reproduction and survival. Average metal residues did not vary significantly between study areas, and with the possible exception of mercury, were present only at background levels. Shells of eggs collected in 1978 were no thinner than eggshells collected before 1947. There was a significant imporvement in mean eggshell thickness from 1970 to 1978 and a corresponding decline in DDE and PCB residues. No deformed or abnormal young were observed. Although elevated levels of industrial contaminants were reported in sediments and sea grasses of Corpus Christi Bay, little of those contaminants appear to have accumulated in the Royal Tern.