Whooping cranes are the tallest and some of the most rare birds in North America. Adults are mostly white and stand almost five feet tall with a wingspan of seven feet. Never an abundant species, the total population dwindled to a low of 16 birds in 1941 due to hunting pressures and habitat loss. Now there are about 600 in the world. These three adults and one juvenile were spotted at Quivira National Wildlife Refuge in Kansas. Photo by Barry Jones, U.S. Fish and Wildlife Service.