Eggs of Black-crowned Night-Herons (Nycticorax nycticorax) were collected in 1979 from two colonies in North Carolina, two colonies in Rhode Island, and one colony in Massachusetts. Mean concentrations of DDE and PCBs were higher in the New England samples than in those from North Carolina, Mean concentrations of organochlorine contaminants in addled eggs collccted at two New England colonies were not significantly different from those in randomly selected eggs. In comparison with the results of a similar study conducted in 1973 at two of the New England colonies, concentrations of DDE in night-heron eggs were lower in 1979, DDD was less frequently detected, DDT and dieldrin were less frequently detected in eggs from one of the two colonies, and eggshell thickness was greater in 1979 for one of the colonies. PCB concentrations in eggs from one colony were lower in 1979 than 1973.
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Organochlorine residues in Atlantic coast black-crowned night-heron eggs, 1979