The Bald Eagle (Haliaeetus leucocephalus Greek hali = salt, aeetus = eagle, leuco = white, cephalis = head) is a bird of prey found in North America. It is the national bird of the United States of America and appears on its Seal. This sea eagle has two known sub-species and forms a species pair with the White-tailed Eagle. Its range includes most of Canada and Alaska, all of the contiguous United States, and northern Mexico. It is found near large bodies of open water with an abundant food supply and old-growth trees for nesting. Its diet consists mainly of fish, but it is an opportunistic feeder. It hunts fish by swooping down and snatching them out of the water with its talons. It is sexually mature at four years or five years of age. The Bald Eagle builds the largest nest of any North American bird, up to 4 meters (13 ft) deep, 2.5 meters (8.2 ft) wide, and one metric ton (1.1 tons) in weight.