Organochlorine pesticide residues in plain Chachalacas from South Texas, 1971-72.

Plain chachalacas (Ortalis vetula) from the intensively cultivated and sprayed Lower Rio Grande Valley of Texas were analyzed for pesticide residues during 1971 and 1972. Residues of eight organochlorine pesticides and a polychlorinated biphenyl were identified in fat tissues of specimens collected from four study areas. Chemicals detected in all 24 birds and average residue levels (+/- SD) in ppm wet weight were: DDT (1.52 +/- 4.12), DDE (2.48 +/- 2.09), dieldrin (0.23 +/- 0.59), endrin (0.13 +/- 0,52), and Aroclor 1248 (0.17 +/- 0.20). Residue levels varied considerably, but the majority of the fat tissues contained significantly less than 1 ppm of these chemicals. Because birds of this species feed primarily on unsprayed native fruits rather than on sprayed crops, they adsorb very few pesticides through their diet. Although birds from exposed areas near cultivated field had generally higher residues than had birds from less exposed areas, these herbivores generally had much lower residues than would most birds living near heavily treated lands. During the present study there was no evidence that plain chachalacas died as a direct result of exposure to agricultural chemicals, nor was there evidence that eggshells of this species have thinned significantly since 1900.