EFFECTS OF ALDRIN EXPOSURE ON SNOW GEESE IN TEXAS RICE FIELDS

In 1972 and 1974, 112 dead or moribund snow geese (Chen caerulescens caerulescens), mostly immature white phase males, were found in a study area on the Garwood Prairie, Texas, USA. Dying geese were observed within 2 days after rice fields planted with insecticide aldrin-treated seed were flooded by heavy rains on 21 March 1972 and 25 March 1974. Brains from 8 snow geese that were moribund when food contained on an average of 8.2 ppm (4.9-14.0 ppm) of dieldrin (a metabolite of aldrin); brains of 14 geese found dead contained an average of 14.1 ppm (2.1-31 ppm). Because no mortalities occurred in 1973 when aldrin-treated rice seed was flooded after all geese migrated or in 1975 and 1976 after the treatment of rice seed with aldrin was suspended, it appears certain that aldrin caused the mortalities.