Black duck (Anas rubripes) eggs were collected in 1971 from the Northeastern United States and Canada. All 61 eggs analyzed contained DDE residues; the mean DDE residues for States and Provinces ranged from 0.09 to 5.94 ppm on a wet-weight basis, with.mean concentrations exceeding 1.0 ppm in eggs from Maine, New York, New Jersey, and Delaware. The highest DDE concentration, 14.0 ppm, was in an egg from Delaware. DDD and DDT residues averaged <0.5 ppm for each collection area. No mirex residues and only trace amounts of dieldrin and heptachlor epoxide were detected. Of the 61 eggs, 57 contained PCB's: mean PCB residues ranged from <0.05 ppm in samples from Nova Scotia to 3.30 ppm in those from Massachusetts. with trace amounts occurring in nearly half the samples. Mean organochlorine pesticide residues appeared to be lower in the 1971 samples than in those analyzed in an earlier study in 1964. The shells from the 61 eggs were measured for thickness. Comparisons of the shell thickness of eggs collected in 1971, 1964, and prior to 1940 showed that the average thickness of shells from eggs collected in 1964 (0.32/ mm) was significantly less (P<0.01) than that of .shells of eggs collected prior to 1940 (0.348 mm) or in 1971 (0.343 mm).
