"They're the bird from hell," says New York fishing guide Tony Buffa. "They deplete our fisheries. They push out more desirable birds. And they spread disease wherever they congregate because they produce so much waste." The U.S. Fish and Wildlife Service (FWS), however, maintains cormorants have only a minor impact on fish populations, and that they are an environmental success story. Pollution, the pesticide DDT, and persecution by humans nearly wiped out cormorants on the Great Lakes in the 1960s. But that changed in the early 1970s, when the Clean Water Act became law, DDT was banned, and cormorants became federally protected under a migratory bird treaty signed with Mexico.