TRANSBOUNDARY POLLUTION - PERSISTENT ORGANOCHLORINE PESTICIDES IN MIGRANT BIRDS OF THE SOUTHWESTERN UNITED-STATES AND MEXICO

The hypothesis that migratory birds accumulate persistent organochlori ne pesticides (POPs) during the winter in Latin America has been preva lent for many years, particularly since 1,1,1-trichloro-2,2-bis(p-chlo rophenyl)ethane (DDT) was banned in the United States in 1972. It has been suggested that peregrine falcons (Falco peregrinus), black-crowne d night herons (Nycticorax nycticorax), white-faced ibises (Plegadis c hihi), various migratory waterfowl and shorebirds, and other avian spe cies accumulate higher concentrations of POPs while on migration or on their wintering grounds in Latin America. Nonetheless, the data obtai ned thus far are limited, and there is no clear pattern to suggest tha t such accumulation occurs on a widespread basis. In this review wildl ife contaminant studies conducted along the U.S.-Mexico border and thr oughout Mexico are discussed. The results for the most part seem to in dicate that no major accumulation of 2,2-bis(p-chlorophenyl)-1,1-dichl oroethylene) (DDE), the most persistent organochlorine compound, has o ccurred or been reported for most parts of Mexico. The majority of the DDE values in birds from Mexico were similar to those reported in bir ds from the southwestern United States during the same years. More wor k needs to be done, particularly in those cotton-producing areas of Me xico where DDT was applied heavily in the past (e.g., Chiapas and Mich oacan). Because DDT is still used for malaria control and may still be used in agriculture in Chiapas, this state is probably the one where most migrant species would still be at a significant risk of increased accumulation of DDE and DDT.