Photo Credit: USFWS Pacific Southwest

A new study conducted by researchers from the Ventana Wildlife Society, the U.S. Fish and Wildlife Service, the Santa Barbara Zoo, the Los Angeles Zoo and Botanical Gardens, and the Bodega Bay Institute found that persistent residues of the pesticide DDT continue to be harmful to birds. The study followed 84 captive-reared California condors released into central California, and compared their reproductive success with nesting condors in interior southern California. They found that egg shells of the central California condors had an average thickness 34 percent lower than the average thickness of southern California condors, and less than half the hatching success rate. The increased reproductive failures of the condors released in central California are thought to have been brought about by exposure to DDT from wastes discharged by a DDT factory along the California coast. Researchers are optimistic that, with enough time, condor populations should recover as DDT contamination continues to decline.