Appearance▲ Back to topThe White-tailed Eagle is a very large bird. It measures 69–95 cm in length with a 1.82–2.44 m wingspan. Females, typically weighing 4–6.9 kg , are slightly larger than males, which weigh 3.1–5.4 kg . The record weight was 7.5 kg for a specimen from Scotland, while a more recent huge female from Greenland reportedly spanned 2.53 m across the wings. The White-tailed Eagle is sometimes considered the fourth largest eagle in the world. It has broad "barn door" wings, a large head and a thick "meat-cleaver" beak. The adult is mainly brown except for the paler head and neck, blackish flight feathers, distinctive white tail, and yellow bill and legs. In juvenile birds the tail and bill are darker, with the tail becoming white with a dark terminal band in sub-adults..
Some individuals have been found to live over 25 years, 21 years on average.
Distribution▲ Back to topThis 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.
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 at the latest, possibly 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 and a tan-headed species. They probably diverged in the North Pacific, spreading westwards into Eurasia and eastwards into North America. Like the third northern species, Steller's Sea Eagle, they have yellow talons, beaks, and eyes in adults.
Reproduction▲ Back to topWhite-tailed Eagles are sexually mature at four or five years of age. They pair for life, though if one dies replacement can occur quickly. A bond is formed when a permanent home range is chosen. They have a characteristic aerial courtship display which culminates in the pair locking talons mid-air and whirling earthwards in series of spectacular cartwheels. White-tailed Eagles are much more vocal than Golden Eagles, particularly during the breeding season and especially the male when near the eyrie. Calls can sometimes take on the form of a duet between the pair.
The nest is a huge edifice of sticks in a tree or on a coastal cliff. Being faithful to their territories, once they breed, nests are often reused, sometimes for decades by successive generations of birds; one nest in Iceland has been in use for over 150 years. In Scandinavia, trees have been known to collapse under the weight of enormous, long established nests.
The territory of the White-tailed Eagle ranges between 30 and 70 km², normally in sheltered coastal locations. Sometimes they are found inland by lakes and along rivers. The territory of the White-tailed Eagles can overlap with the territory of the Golden Eagle, and competition between the two species is limited. Golden Eagles prefer mountains and moorland, while the White-tailed Eagle prefers the coast and the sea. In adulthood, the White-tailed Eagle has no natural predators and is thus considered an apex predator.
Mated pairs produce one to three eggs per year. The eggs are laid two to five days apart in March or April and are incubated for 38 days by both parents. Once hatched, chicks are quite tolerant of one another, although the first hatched is often larger and dominant at feeding times. The female does most of the brooding and direct feeding, with the male taking over now and then. Young are able to feed themselves from five to six weeks and they fledge at eleven to twelve weeks, remaining in the vicinity of the nest, dependent on their parents for a further six to ten weeks. The sex of nestlings can be identified using field methods, or using DNA.
Surplus chicks are sometimes removed from nests to use in reintroduction programs in areas where the species has died out. If left in the nest, they are often killed by the first-hatched sooner or later, as in most large eagles.
In such programs, the birds are raised in boxes on platforms in the tree canopy and fed in such a way that they cannot see the person supplying their food, until they are old enough to fly and thus find their own food.
Food▲ Back to topThe Eagle's diet is varied, including fish, birds, carrion, and, occasionally, mammals. Many birds live largely as scavengers, regularly pirating food from otters and other birds, and carrion is often the primary food source during lean winter months. However, this eagle can be a powerful hunter as well. Locally, this species may compete fiercely with Golden Eagles over the rabbits and hares either eagle may catch. The daily food requirement is in the region of 500-600 g. Although a less active hunter than the Golden Eagle, competition over food can go either way depending on the individual eagle. They can exist at higher population densities and typically outnumber Golden Eagles because of their longer gut and more efficient digestive system, being able to live better with less food.
In the Baltic, the diet of the sea eagle consists mainly of sea birds and pike. Recently they are reported to have attacked and eaten Great Cormorants and in some cases destroyed whole colonies. In the UK, fulmar are noted as a common prey species and may contribute to locally high levels of DDT and PCB chemicals in nesting birds.
Evolution▲ Back to topOn Orkney Scotland, sea eagle bones have been found in 6000 year old burial mounds, suggesting that the birds were revered by the prehistoric people there, a belief strengthened by the Pictish stone carvings of sea eagles from Orkney.
Cultural▲ Back to topIn the Shetland Isles Scotland, fishermen believed that as soon as a sea eagle appeared fish would rise to the surface, belly up; this led to some fishermen using eagle fat, smeared on their bait, to increase their catch.
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