Steller's Sea Eagle
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| Steller's Sea-eagle | ||||||||||||||
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| Haliaeetus pelagicus (Pallas, 1811) |
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 Red: breeding only
Green: resident all year Dark blue: winter only Light blue: vagrant range. |
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see text |
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Aquila pelagica |
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 to 9 kg (15 - 20 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 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.
[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 up 9 kg (15 to up 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, who apparently 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 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.
[edit] Food
The Steller's Sea-eagle mainly feeds on fish, especially salmon and trout. Besides fish, 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 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.
[edit] Gallery
 Adult |
 Adult back |
 Juvenile right side |
 Juvenile left side |
 Juvenile head |
 Feathers on the head |
[edit] References
- BirdLife International (2004). Haliaeetus pelagicus. 2006 IUCN Red List of Threatened Species. IUCN 2006. 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
[edit] Footnotes
- ^ Etymology: Haliaeetus, New Latin for "sea-eagle". pelagicus, "of the open seas", from Ancient Greek pelagos, the ocean.
- ^ Etymology: niger, Latin for "black".
[edit] External links
- BirdLife Species Factsheet. Retrieved 2006-DEC-01.
- Biocrawler.com: Windows Media streaming video showing Haliaeetus pelagicus. Retrieved 2006-DEC-01.
- Arkive.org: Real Media streaming video showing Haliaeetus pelagicus. Retrieved 2006-DEC-01.
- Natural Research Ltd.: Steller's Sea Eagle Studies. Retrieved 2006-DEC-01.
