Steller's Sea Eagle

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iSteller's Sea-eagle
Steller's Sea-eagle in Berlin Zoo
Steller's Sea-eagle in Berlin Zoo
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Falconiformes
Family: Accipitridae
Genus: Haliaeetus
Species: H. pelagicus
Binomial name
Haliaeetus pelagicus
(Pallas, 1811)
Red: breeding onlyGreen: resident all yearDark blue: winter onlyLight blue: vagrant range.
Red: breeding only
Green: resident all year
Dark blue: winter only
Light blue: vagrant range.
Subspecies

see text
Synonyms

Aquila pelagica
Pallas, 1811

The Steller's Sea-eagle (Haliaeetus pelagicus[1]) is a large bird of prey in the family Accipitridae which also includes many other diurnal raptors such as kites, buzzards and harriers. This is, on average, the heaviest eagle in the world, as it averages about 6.8 kg (15 lb), but may lag behind the Harpy Eagle and the Philippine Eagle in other measurements.

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 Hokkaido, Japan. That being said, Steller's Sea-eagle is less vagrant than the White-tailed Eagle, usually lacking the long-range dispersal common in juveniles of that species.

[edit] 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 86.5-105 cm (34-41 inches) long and the wingspan is 203-241 cm (6.8-8 feet). On average, females weigh from 6.8 to 9 kg (15 to 20 lb), while males are considerably lighter with a weight range from 4.9 to 6 kg (10.8 to 13.2 lb). An unverified record exists of a huge female, gorged on salmon, having weighed 12.7 kg (28 lb).

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.

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.(Wink et al., 1996)

The large size (see also Bergmann's Rule) suggests that it is a glacial relict, 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.

[edit] Food

Steller's Sea-eagle mainly feeds on fish, especially salmon and trout. Besides this, it also preys on water dwelling birds, mammals and carrion. This eagle may prey on young seals, but seals are generally more likely to be eaten as carrion.

[edit] 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. At an age of around ten weeks, the young birds learn to fly, while they reach sexual maturity at around four to five years. Only at the age from eight to ten years a Steller's Sea Eagle is wearing full adult plumage.

[edit] References

  • BirdLife International (2004). Haliaeetus pelagicus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 06 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
  • 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

[edit] Footnotes

  1. ^ Etymology: Haliaeetus, New Latin for "sea-eagle". pelagicus, "of the open seas", from Ancient Greek pelagos, the ocean.
  2. ^ Etymology: niger, Latin for "black".

[edit] External links

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