Nationwide monitoring of organochlorine and mercury residues in wings of approximately 5,200 adult mallards and black (ducks bagged during the 1969-70 hunting season showed DDE, as in 1965 and 1966, to be the predominant residue. PCB's were next in overall prevalence, followed by mercury, DDT, dieldrin, DDD, and heptachlor epoxide. There was no indication of a decrease in levels from 1966. Residues were generally highest in the Atlantic and Pacific Flyways and lowest in the Central Flyway; PCB's, however, were highest in the Atlantic Flyway and diminished westward across the Nation. Mercury residues were highest in A tlantic Flyway black ducks. Monitoring results were consistent: States with high residues in 1965 and 1966 were again high in 1969. Analyses of individual wings of mallards from California and black ducks from New Jersey and New York revealed DDE residues as high as 41 ppm and certain regional and seasonal differences in levels within States. They also revealed an apparent tendency for DDE residues to be more variable and to attain higher levels in male than in female wings.
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Nationwide organochlorine and mercury residues in wings of adult mallard and black ducks during the 1969-70 hunting season