Monday, April 9, 2012

Bald eagles

The bald eagle is the largest raptor in Utah and second only to the Condor in North America. As with most raptors, the female is larger than the male. Males may weigh as little as 4.5 pounds and the largest females may weigh up to 14 pounds. The wingspan is 6.5-8 feet and the body may be up to 36 inches long. Bald eagles from the northern parts of their range are usually much larger then the southern birds. The adult plumage is attained gradually over a 4-5 year period and is dark brown on the body with a white head and tail. Male and females have the same coloring. The large beak, eyes and feet are bright yellow. First-year juvenile birds have a dark brown plumage mottled with white, particularly on the underparts. The beak and eyes of the juvenile are dark brown and gradually change to yellow as the bird matures.

Bald eagles are large, aggressive, vocal raptors who often use communal roost sites except during the breeding season. Although very efficient hunters, bald eagles are very piratical in their feeding habits, and often steal prey from other birds. They are usually migratory and are commonly found along waterways. In Utah, they arrive in November and typically stay until the end of February. Bald eagles that winter in Utah return to western Canada in the spring. Bald eagles generally return to traditional breeding sites in the spring of the year.


Bald eagles in the southern United States may nest as early as December, while in the northern parts of their range, they may nest as late as May. They mate for life. Aerial courtship displays often include "talon grappling", a series of descending somersaults the pair performs with their feet locked together. Nests are generally used year after year, and may reach enormous proportions. One nest measured 8.5 feet in diameter, was 12 feet tall and weighed an estimated 8.5 tons. Nests are most often built in trees but may be found on cliffs or even on the ground in treeless areas. 2-3 large eggs are laid in the grass or seaweed-lined nest and are incubated for 35 days. The first eaglet to hatch may contribute to sibling mortality either by pushing them out of the nest or by eating most of the food brought by the adults. Eaglets generally take their first flight at 2.5-3 months of age and the parental care period continues for the next 2-3 months.

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