Dieldrin and endrin residues in fulvous whistling-ducks in Texas in 1983

Fulvous Whistling-Ducks were collected near nesting areas in the rice fields of Texas in 1983 to determine if these birds continue to carry residue levels of organochlorine contaminants, and if the contaminants were acquired in Texas or Mexico. Adults were collected immediately after they arrived from wintering grounds and juveniles were collected in late summer before their departure to wintering grounds. Carcasses of 7 of 15 adults, some of which had been feeding in rice fields, contained residues of dieldrin in low to moderately high levels and 4 contained low levels of endrin. None of 16 flightless juveniles contained organochlorine residues. The contaminated adults were most likely exposed to aldrin or dieldrin via illegal treatment of rice seed with aldrin in some nesting areas of Texas.