White-tailed sea-eagle, Ern, Erne, Gray sea eagle, Eurasian sea eagle
The White-tailed eagle (Haliaeetus albicilla ) is one of the largest living birds of prey. It is sometimes considered the fourth largest eagle in the world and is on average the fourth heaviest eagle in the world. White-tailed eagles are considered a close cousin of the Bald eagle, which occupies a similar niche in North America.
The adult White-tailed eagle is a greyish-mid-brown color overall. The plumage is fairly uniform over most of the body and wings, but the upper wing coverts are typically somewhat paler. In the adult, the head, neck, and upper breast have a distinctly paler appearance than the rest of the plumage and most often have a buff coloration. Some of the palest birds can appear anywhere from cream-tawny to light grayish. When many of the feathers are freshly molted, they can take on a slight purplish gloss. The brownish hue of the adult overall makes the somewhat wedge-shaped white tail stand out in contrast. All the bare parts of the adult's body are yellow in color, including the bill, cere, feet, and eyes. Juvenile and immature White-tailed eagles are a much darker brown than the adults and are more unevenly marked, with whitish feather edgings variably showing, mostly manifesting in some small areas of the underside and under-wing, with a narrow white axillary strip usually apparent. The upperside is usually similarly darkish brown but variable based on the extent of blackish-brown tip to otherwise buff-brown feathers of the mantle, back, and upper wing. The head of the juvenile is normally a blackish-brown hue, somewhat darker, and always more uniform than most of the other feathers. The juvenile's tail tends to be a washed-out greyish-cream color with messy blackish color on the feather edges and on the tips. The bill of juveniles is usually almost half dark brown from the tip and half dirty, dull yellowish or gray to the base, while the feet are usually a dirty yellow and the eyes are a darkish brown.
White-tailed eagles are widely distributed in northern Europe and northern Asia. They may be considered partial migrants. They seldom migrate in the western part of their range, and eagles that breed as far north as Greenland, Iceland, and coastal Norway do not move at all for winter. These birds live in varied habitats but usually are closely associated with water and generally occur in lowland areas. Especially in winter, many White-tailed eagles often frequent low coastal spots, estuaries, and coastal marshes. Inland, birds usually require secluded woods, forested areas, or groups of trees with tall mature trees and access to freshwater wetlands such as lakes, river systems, marshes, or extensive, low-disturbance farmland.
White-tailed eagles are diurnal and spend much of their day perched on trees or crags, and may often not move for hours. Pairs regularly roost together, often near their nest, either on a crag or tree or crevices, overhung ledges, or small isolated trees on a crag. While a relatively gregarious raptor, White-tailed eagles are territorial and any intrusion often provokes vigorous fighting, in which either combatant can even die. During winter, migrating White-tailed eagles tend to become gregarious, especially younger juvenile birds. Many such groups can contain up to 10 birds and, in areas near large breeding populations - at least 30-40 individuals. White-tailed eagles are powerful predators and hunt mostly from perches, in a “sit-and-wait” style, usually from a prominent tree perch. Fish is usually grabbed in a shallow dive after a short distance flight from a perch, usually with the eagles only getting their feet wet. At times they will also fish by wading into shallows, often from shores or gravel islands. When it comes to non-fish prey, White-tailed eagles often hunt by flying low over sea coast or lake shore and attempting to surprise victims. White-tailed eagles become very vocal during the breeding season. The male call is 'gri-gri-gri' or 'krick-krick-krick', while the female is a deeper 'gra-gra-gra-gra' or 'krau-krau-krau-krau'. Often pairs will duet during early spring, in flight, or from a perch. Alarm calls tend to be 3-4 short, loud 'klee' or 'klek' notes.
White-tailed eagles are carnivores but also scavengers. Their diet consists mainly of fish and water birds but also small mammals. Carrion is often the primary food source during winter months.
White-tailed eagles are monogamous and pairs mate for life. The breeding season occurs from January to July in the south of their range, and from April to September in the northern part of their range. Pairs frequently engage during early spring variously in soaring, sky-dancing, and other aerial displays, all with much loud calling, often performed by pair members together, including spectacular mutual cartwheel downwards where talons touch or interlock. White-tailed eagles usually nest in large trees and nests may be in a high main fork, on the canopy, or on a large side branch. Nests are usually huge, constructed of sticks and branches, averaging roughly 1 m (3.3 ft) across and up to 2 m (6.6 ft) deep, lined variously with moss, greenery, seaweed, or wool. The female lays 2 broad oval shape and dull white in color eggs which she incubates between 38 and 42 days. Hatchlings have a creamy white down which is longest and whitest on the head and often dirty grayish on wings and rump. They are able to move around the nest 10 days after hatching and fledge at 70-80 days of age. They become independent 1 or 2 months later and reach reproductive maturity at 5 to 6 years of age.
For many years White-tailed eagles have been threatened mainly due to human activities. These have included habitat alterations and destruction of wetlands, about a hundred years of systematic persecution by humans followed by inadvertent poisonings and epidemics of nesting failures due to various manmade chemical pesticides and organic compounds, which have threatened eagles since roughly the 1950s and continue to be a potential concern. Due to this, White-tailed eagles were considered endangered or extinct in several countries. These beautiful birds still suffer from illegal persecution by gamebird shooting and egg thieves, habitat loss, deforestation, pollution, accidental poisoning, and collision with wind generators and wind turbines.
According to the IUCN Red List, the total White-tailed eagle population size is around 20,000-49,999 mature individuals. In Europe, the breeding population consists of 9,000-12,300 breeding pairs, equating to 17,900-24,500 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
