It is not known when the cranes were shot. They were part of the Whooping Crane Eastern Partnership, an initiative aimed at reintroducing whooping cranes into the eastern United States. There are about 570 whooping cranes left in the world, 400 of them in the wild, according to the Fish and Wildlife Service. About 100 cranes are in the eastern migratory population. This was the cranes' first migration, the service said in a statement. They were banded and equipped with transmitters and had last been tracked in Hamilton County, Tennessee, where they roosted with other cranes December 10.