Once a common sight in the forests of the eastern United States, the cerulean warbler is vanishing at an alarming rate. Since 1966 its numbers have declined by 70 percent, due primarily to habitat fragmentation and destruction in both its breeding and winter ranges. In October 2000, 28 conservation organizations, including Defenders of Wildlife, petitioned the U.S. Fish and Wildlife Service to list this species as threatened under the Endangered Species Act. To date, the Service has not taken any action.