The Bald Eagle is a large bird, with a body length of 70–102 centimeters (28–40 in), a wingspan of up to 2.44 m (96 in), and a mass of 2.5–7 kilograms (5.5–15 lb); females are about 25 percent larger than males. The adult Bald Eagle has a brown body with a white head and tail, bright yellow irises, and golden taloned feet and hooked beak; juveniles are completely brown except for the yellow feet. Males and females are identical in plumage coloration. Its diet consists mainly of fish, but it is an opportunistic feeder. It hunts fish by swooping down and snatching the fish out of the water with its talons. It is sexually mature at four years or five years of age. In the wild, Bald Eagles can live up to thirty years, and often survive longer in captivity. 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.