Pesticide mortality of young white-faced ibis in Texas

The combination of the symptoms observed in sick and dying birds and the high brain residues in the three birds collected dying, as well as in two of the four collected dead, implicate dieldrin as at least one of the causes of mortality of young ibis at the Lavaca Bay colony. Mercury residues in the kidneys of all four dead young, including those with low brain residues of dieldrin, suggest that birds were exposed to mercury in rice fields and that mercury may also have contributed to the mortality. Since adult ibis normally feed their young on invertebrates collected in rice fields treated with aldrin and Ceresan L, the use of these rice pesticides appears to be a serious hazard to this species, and probably to other wild birds with similar habits.