Steller's Sea Eagle

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Image:StellersSeaEagle.jpg

Common Name: Steller's Sea Eagle
Scientific Name: Haliaeetus pelagicus

Size: 33-41 inches (85-105 cm); Wingspan: 84-87 inches (213-220 cm)

Habitat: Asia; breeding range extends from 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 farther south, in the southern Kuril Islands, Russia and Hokkaidō, Japan. Vagrant eagles have been found in North America, at locations including the Pribilof Islands and Kodiak Island, inland to as far as Peking in China and Yakutsk in Russia's Sakha Republic, and south to as far as Taiwan, but these are considered to be individual eagles that have strayed far from the species' typical range.

They prefer sea coasts and large rivers with mature trees. The timing, duration, and extent of migration depends on ice conditions and food availability. On Kamchatka, eagles overwinter in forests and river valleys near the coast, but are irregularly distributed over the peninsula. Most wintering birds there appear to be residential adults. Steller's sea eagles that do migrate fly down to winter in rivers and wetlands in Japan, but will occasionally move to mountainous inland areas as opposed to the sea coast. Each winter, drifting ice on the Sea of Okhotsk drives thousands of eagles south. Ice reaches Hokkaido in late January. Eagle numbers peak in the Nemuro Strait in late February. On Hokkaido, eagles concentrate in coastal areas and on lakes near the coast, along with substantial numbers of white-tailed eagles. Eagles depart between late March and late April, adults typically leaving before immatures. Migrants tend to follow sea coasts and are usually observed flying singly. In groups, migrants are typically observed flying 100–200 m (330–660 ft) apart. On Kamchatka, most migrants are birds in transitional plumages. They are also occasionally seen flying over the northern ocean or perching on sea ice during the winter.

Status: Vulnerable. Global population: 5,000 adult individuals with a decreasing population trend. Despite being legally protected, being classified as a National Treasure in Japan and mostly occurring in protected areas in Russia, many threats to their survival persist. These mainly include habitat alteration, industrial pollution, and over fishing, which in turn decrease their prey source. The current population is estimated at 5,000 and decreasing. It was observed that recent heavy flooding, which may have been an effect of global climate change, caused almost complete nesting failure for the eagles nesting in Russian rivers due to completely hampering the ability of the parents to capture the fish essential to their nestlings' survival. Persecution of the bird in Russia continues, due to its habit of stealing furbearers from trappers. Due to a lack of other accessible prey in some areas, increasingly, eagles on Hokkaido have moved inland and scavenged on sika deer carcasses left by hunters, exposing them to a risk of lead poisoning through ingestion of lead shot.

Diet: Mainly feeds on fish. Their favored prey in river habitats are salmon (Oncorhynchus spp.) and trout. Among these, pink salmon (O. gorbuscha) and chum salmon (O. keta) are favored, sometimes intensely supplemented by grayling (Thymallus thymallus) and three-spined stickleback (Gastrossteus aculeatus). Fish comprise about 80% of the diet of eagles; other prey consists largely of water-dwelling birds, including ducks, geese, swans, cranes, herons, and gulls.

Most often, Steller's sea eagles hunt from a perch in a tree or rocky ledge located 5–30 m (16–98 ft) above the water. When prey is spotted, the bird dives from its perch. Eagles may also hunt on the wing, while circling 6–7 m (20–23 ft) above the water. Again, prey is captured by diving. Eagles sometimes hunt by standing in or near shallow water on a sandbank, spit, or ice-flow, grabbing passing fish. Steller's sea eagles are more aggressive than their white-tailed and bald eagle relatives.

Nesting: The sexes are similar although females are significantly larger and heavier than males. Mature sea eagles are dark brown to black over the majority of their bodies, with strongly contrasting white on the lesser and median upper-wing coverts, under wing coverts, thighs, under-tail coverts and tail. Their wedge-shaped, white tails 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. The eyes, the bill, and the feet of adults are all yellow in coloration.

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 gray-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.

Courtship, which usually occurs between February and March, is reported to consist of a simple, soaring flight above the breeding area.

It builds several aeries, being bulky constructions of twigs and sticks, at a height up to 150 cm (59 in) and diameter up to 250 cm (98 in). They usually place such nests high up on trees and rock at 15 to 20 m (49 to 66 ft) above the ground, sometimes in trees up to 45 m (148 ft). Alternate nests are usually built within 900 m (3,000 ft) of each other. In one case, two active nests were found to have been located within 100 m (330 ft).

The Steller's sea eagle copulate on the nest after building it. They lay their first greenish-white eggs around April to May. Clutches can contain from one to three eggs, with two being the average. Usually, only one chick survives to adulthood, though in some cases as many as three will successfully fledge. Incubation begins with the first hatching, which occurs in mid-May to late June. After an incubation period which is approximately 39 – 45 days, the whitish-down covered chicks hatch. The eaglets fledge in August or early September. Adult plumage is attained at four years of age, but first breeding does not typically occur for another year or two.

Cool Facts: It has sometimes been referred to as the Pacific eagle or white-shouldered eagle. In Russian, the eagle has been called morskoi orel (sea eagle), pestryi morskoi orel (mottled sea eagle) or beloplechii orlan (white-shouldered eagle). In Japanese, it is called 0-washi (large eagle or great eagle).

There are two subspecies of Stellars’ Sea Eagle:

  • H. p. pelagicus. The relatively widespread nominate.
  • H. p. niger. This subspecies lacks 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 might be an extremely rare morph rather than a valid subspecies.



Found in Songbird ReMix Birds of Prey Volume 5: Falcons, Hawks & Eagles

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