White-tailed Eagle - Distribution and Systematics

Distribution and Systematics

This large eagle breeds in northern Europe and northern Asia. The largest population in Europe is found along the coast of Norway. The World population in 2008 stands at only 9,000–11,000 pairs. They are mostly resident, only the northernmost birds such as the eastern Scandinavian and Siberian population migrating south in winter. Birds from eastern Russia rarely vagrate into Alaska.

Small disjunct resident populations occur in southwesternmost Greenland and western Iceland. The former has been proposed as a distinct subspecies groenlandicus based on their very large size and body proportions. However, the species is now considered monotypic and the size variation is clinal according to Bergmann's Rule. A recent genetic study of mitochondrial DNA is consistent with this idea. Greenlandic white-tailed eagles are, on evolutionary time scales, a relatively recently founded population that has not yet accumulated a lot of unique genetic characteristics. However, the population appears to be demographically isolated and deserves special protection.

The White-tailed Eagle forms a species pair with the Bald Eagle. These diverged from other sea eagles at the beginning of the early Miocene (c. 10 mya) at the latest, possibly (if the most ancient fossil record is correctly assigned to this genus) as early as the early or middle Oligocene, about 28 mya ago.

As in other sea-eagle species pairs, this one consists of a white-headed (the Bald Eagle) and a tan-headed species. They probably diverged in the North Pacific, spreading westwards into Eurasia and eastwards into North America. Like the third large northern species, Steller's Sea Eagle, they have yellow talons, beaks, and eyes in adults.