The Steller’s Sea Eagle (Haliaeetus pelagicus)  is a large bird of prey in the family Accipitridae. It is an eagle that lives in coastal northeastern Asia and mainly preys on fish and water birds. On average, it is the heaviest eagle in the world, at about 5 to 9 kilograms (11 to 20 lb; 0.79 to 1.42 st), but may lag behind the Harpy Eagle (Harpia harpyja) and Philippine Eagle (Pithecophaga jefferyi) in some standard measurements. This bird is named after the German naturalist Georg Wilhelm Steller.
Steller’s Sea-eagle is the biggest bird in the genus Haliaeetus and is one of the largest raptors overall. Females typically weigh from 6.8 to 9 kilograms (15 to 20 lb; 1.07 to 1.42 st), with an average of 7.6 kilograms (17 lb; 1.20 st) while males are rather lighter with a weight range from 4.9 to 6 kilograms (11 to 13 lb; 0.77 to 0.94 st). At its average weight, the Steller’s outweighs both the average Harpy and the average Philippine Eagles by over 0.5 kilograms (1.1 lb; 0.079 st). The Steller’s Sea Eagle’s can range in total length from 85 to 105 cm (33 to 41 in). The wingspan is from 1.95 to 2.5 m (6.4 to 8.2 ft) and the wing chord measurement is 57–68 cm (22–27 in). The Steller’s sea eagle has the second largest median wingspan of any eagle. Both the wing chord and wingspan, at an average of 2.13 m (7.0 ft), are similar or slightly smaller than to those of the Steller’s close relative, the White-tailed Eagle (Haliaeetus albicilla), which is nonetheless rather smaller in both weight and total length. As in mostHaliaeetus eagles, the tarsus and the tail in this species are relatively short compared to other very large eagles at 9.5–10 cm (3.7–3.9 in) and 32–39 cm (13–15 in) in length, respectively. The bill is very large. In fact, the skull (at around 14.6 cm (5.7 in)) and the culmen (at around 7 cm (2.8 in)) of the Steller’s Sea Eagle are the largest of any eagle and are comparable in size to those of the largest accipitrids, the Old World vultures.
The Steller’s Sea Eagle is dark brown to black over the majority of its body, with strongly contrasting white on the lesser and median upper-wing coverts, underwing coverts, thighs, under-tail coverts and tail. They have wedge-shaped, white tails that are relatively longer than those of the White-tailed Eagle. The bold, pied coloration of adults may play some part in social hierarchies with other eagles of their own species during the non-breeding season, although this has not been extensively studied. The eyes, the bill and the feet of adults are all yellow in coloration. Two subspecies have been named: The relatively widespread nominate pelagicus and the virtually unknown H. p. niger. The latter name was given to the population which lacked white feathers except for the tail and supposedly was resident all year in Korea. Last seen in 1968 and long believed to be extinct, a female matching H. p. niger in appearance was born in captivity in 2001. Both its parent were “normal” in appearance, indicating that H. p. niger is an extremely rare morph rather than a valid subspecies, as had already been suggested earlier.
The first down plumage of new nestlings is silky white, though they soon turn a smoky brown-gray. As in other sea eagles, remiges and retrices of the first-year plumage are longer than adults. Juvenile plumage is largely a uniform dark brown with occasional grey-brown streaking about the head and the neck, white feather bases and light mottling on the retrices. The tail of the immature eagle is white with black mottling basally. The young Steller’s Sea Eagle has a dark brown iris, whitish legs and blackish-brown beak. Through at least three intermediate plumages, mottling in the tail decreases, body and wing feathering acquires a bronze cast, and the eye and bill lighten in color. Definitive plumage is probably reached in the fifth year of life, based on fragmentary data from captives. First and intermediate plumages are difficult to distinguish from those of the White-tailed Eagle, which occurs in the entire breeding range of the Steller’s.
Steller’s Sea Eagles are not extensively known for their voices but are known to make a deep barking cry, ra-ra-ra-raurau, in aggressive interactions. Their call is similar to the White-tailed Eagles but deeper. During the display at the beginning of the breeding season, they have been heard to make calls to each that sound like very loud, deep-voiced gulls. Wikipedia