Residues of organochlorine compounds occur commonly in environmental samples and have been associated with adverse effects in numerous avian species. The affected species are usually terminal consumers, generally those feeding on aquatic organisms (primarily fish) or birds. Brown Pelicans (Pelecanus occidentalis), Double-crested Cormorants (Phalacrocorax auritus , and certain herons are among the species that have exhibited shell thinning in some regions. In 1972, we began a study to determine: (1) geographic differences in the occurrence of environmental pollutants in Anhingas (Anhinga anhinga) and waders in the eastern United States; (2) differences in environmental pollutant levels among those species nesting at the same localities; and (3) whether eggshell thickness had changed since the widespread use of organochlorine pesticides began in the mid-1940's.
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Organochlorine residues and eggshell thinning in anhingas and waders