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Steller's Sea-eagle
At San Diego Zoo, USA
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Falconiformes (or Accipitriformes, q.v.)
Family: Accipitridae
Genus: Haliaeetus
Species: H. pelagicus
Binomial name
Haliaeetus pelagicus
(Pallas, 1811)
Subspecies

see text

Orange: breeding only
Green: resident all year
Blue: winter only
Purple: vagrant range.
Synonyms

Aquila pelagica
Pallas, 1811

The Steller's Sea Eagle, Haliaeetus pelagicus,[1] is a large bird of prey in the family Accipitridae. It lives in coastal northeastern Asia and mainly preys on fish. It is, on average, the heaviest eagle in the world, at about 4.9 to 9 kilograms (11 to 20 lb; 0.77 to 1.42 st), but often lags behind the Harpy Eagle and the Philippine Eagle in other measurements. This bird is named after the German naturalist Georg Wilhelm Steller, and two subspecies have been named.

The size of this animal can be gauged by comparison to the human.

Description, systematics, and status

Stellers' Sea-eagle is the biggest bird in the Genus Haliaeetus and is one of the largest raptors overall. The typical size range is 86.5 to 105 centimetres (34.1 to 41.3 in) long and the wingspan is 203 to 241 centimetres (80 to 95 in). On average, females weigh from 6.8 to 9 kilograms (15 to 20 lb; 1.07 to 1.42 st), while males are considerably lighter with a weight range from 4.9 to 6 kilograms (11 to 13 lb; 0.77 to 0.94 st). An unverified record exists of a huge female, who apparently gorged on salmon, having weighed 12.7 kilograms (28 lb; 2.00 st). Two subspecies have been named: the nominate pelagicus, and the Korean Sea-eagle, Haliaeetus pelagicus niger.[2] The latter name was given to the Korean population which was apparently resident all year and lacked white feathers except for the tail. Its validity is disputed; it may have been a morph and not a genetically distinct population. In any case, the Korean population of this species is extinct since the 1950s due to habitat loss and hunting.

The relationships of Steller's Sea-eagle are not completely resolved. mtDNA cytochrome b sequence data tentatively suggests that this species's ancestors diverged early in the colonization of the Holarctic by sea eagles. This is strongly supported by morphological traits such as the yellow eyes, beak, and talons shared by this species and the other northern sea-eagles, the White-tailed and Bald Eagles, and biogeography.[3]

Distribution and habitat

This bird breeds on the Kamchatka Peninsula, the coastal area around the Sea of Okhotsk, the lower reaches of the Amur river and on northern Sakhalin and the Shantar Islands, Russia. The majority of birds winter further south, in the southern Kuril islands and Hokkaidō, Japan. That being said, the Steller's Sea-eagle is less vagrant than the White-tailed Eagle, usually lacking the long-range dispersal common in juveniles of that species.

These stunning birds live in the Eastern Part of Russia in the snowy cold climate areas. Each Winter these birds migrate to Japan so they do not freeze to death. But these places must be near open water because that is where these eagles get their food.

The large size (see also Bergmann's Rule) suggests that it is a glacial relic, meaning that it evolved in a narrow subarctic zone of the northeasternmost Asian coasts, which shifted its latitude according to ice age cycles, and never occurred anywhere else. It is unique among all sea eagles in having a yellow bill even in juvenile birds, and possessing 14, not 12, rectrices. The skull and bill are the largest of any eagle and comparable to the largest Old World vultures, the biggest accipitrids.[4]

The birds have been found in North America but this is considered to be individual eagles that for various reasons have strayed too far from Asia, rather than actually being native to North America.

This species is classified as Vulnerable. The main threats to its survival are habitat alteration, industrial pollution and over-fishing. The current population is estimated at 5,000 and decreasing.

Steller's Sea Eagle Haliaeetus pelagicus Head Fluffed 2600px.jpg

Diet

The Steller's Sea-eagle mainly feeds on fish. Favored prey include salmon (Onchorhynchus spp.), trout and cod.[5] Besides fish, it also preys on water-dwelling birds (including ducks, geese, swans and gulls), mammals, crabs, squid and carrion.[6] This eagle may prey on young seals, but seals are generally more likely to be eaten as carrion.

Reproduction

This eagle builds several aeries (height, 150 cm; diameter up to 250 cm) high up on trees and rock. It is possible that the eagles change occasionally between these nests.

After courtship, which usually occurs between February and March, the animals lay their first white-green eggs around April to May. Usually only one chick survives. After an incubation period of around 39 – 45 days the chicks hatch, having ash grey to white down. As young birds the down changes to brown feathers and at an age of around ten weeks, the young birds learn to fly. They reach sexual maturity at around four to five years. Full adult plumage in the Steller's Sea Eagle only appears at age eight to ten years.

Eggs and nestlings can be preyed on by arboreal mammals, such as martens, and birds, usually corvids. Once fully grown, the eagle has no natural predators.[7] They are at the top of the avian food chain.

Gallery

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References

Bibliography

  • BirdLife International (2004). Haliaeetus pelagicus. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 6 May 2006. Database entry includes a range map, a brief justification of why this species is vulnerable, and the criteria used
  • Brown, Leslie Hilton (1976): Eagles of the world. David & Charles, Newton Abbot. ISBN 0-7153-7269-6
  • Ferguson-Lees, James; Christie, David A. & Franklin, Kim (2005): Raptors of the world: a field guide. Christopher Helm, London & Princeton. ISBN 0-7136-6957-8
  • True, Dan (1980): A family of eagles. Everest, New York. ISBN 0-89696-078-1
  • Wink, M.; Heidrich, P. & Fentzloff, C. (1996): A mtDNA phylogeny of sea eagles (genus Haliaeetus) based on nucleotide sequences of the cytochrome b gene. Biochemical Systematics and Ecology 24: 783-791. doi:10.1016/S0305-1978(96)00049-X PDF fulltext

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