Members of the genus Haliaeetus are large to very large eagles, with long, broad wings and medium to short rounded or wedge-shaped tails. The bill is large, strong and compressed. The legs are short and the toes and talons powerfully developed
Listen to the sound of Stellers Sea Eagle
[audio:http://www.planetofbirds.com/MASTER/ACCIPITRIFORMES/Accipitridae/sounds/Stellers Sea Eagle.mp3]
Copyright remark: Most sounds derived from xeno-canto
Nests are always found near the mouths of rivers, in river valleys, along sea coasts, or on lakes. Nesting is most common in the coastal zone, where rocky shorelines, timbered river valleys, bays, and inlets are preferred. In the interior, nesting occurs less frequently in river valleys and on lakes. On Kamchatka, park-like stands ofErmann’s birch (Betula ermani) and floodplain alder-willow-poplar forests (Ainus. Salix. Populus spp.) are preferred. On the east coast, nests are usually within 30 km of the coast, but a few are 50 km or more inland. On the west coast, many pairs nest 50-80 km from the sea. Elsewhere in the range, nests on major rivers may be 100 km or more inland. Throughout the range, nests usually are in trees and occasionally on cliffs. On Kamchatka, nests are built most often in poplar and birch. All nests in the lower Amur and most on the Sea of Okhotsk and Sakhalin Island are in larches (Larix spp). Nests are typically in the tops of large, mature trees, usually with a dead top. Less often nests are constructed in healthy trees. Nests may be 15-20 m from the ground. Nests are often used for several years in succession, but alternate nests are often built, usually within 900 m of the previous nest. Nests are bulky, constucted of thick branches and twigs, and may reach 2 m in diameter. On one occasion, 2 occupied nests were only 100 m apart.
Breeding success appears to be poor. In any given year on Kamchatka, 45-67% of eggs produced will fail to produce young to fledging, and up to 27% of nestlings will be lost. Failed nesting attempts occur most often due to predation (sable and ermine) and collapsing nests. No nests with 3 fledging-age young have been recorded. All of the breeding range is shared with H. albicilla. Prey and habitat preferences of both species are the same, but on Kamchatka the congener predominates in places where H. pelagicus is rare or sporadic. Where the two species do occur together, H. pelagicus. the larger of the two, seems to accept the former’s presence.
Three hunting techniques and pirating have been observed. Most often, eagles hunt from a perch in a tree or rocky ledge 5-30 m 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 above the water. Again, prey is captured by diving. Eagles sometimes hunt by standing in shallow water on a sandbank, spit, or ice-flow, grabbing passing fish. Where feeding occurs in groups, kleptoparasitism is common. Kleptoparasitism is most beneficial in procuring food during periods of food abundance and in large feeding aggregations. Immatures use kleptoparasitism as much as adults, but are attacked more often by adults than birds of similar age. Adults appear to benefit most from this behavior. The bold color patterns of adults may be an important signal influencing the formation of feeding groups. Outside the breeding period, birds probably roost communally near their feeding sites.
On the lower reaches of the Amur River, summer diet consists of about 80% fish, 10% birds, and 5% mammals. Invertebrates (crabs, sea urchins, mussels, and squid) washed up on shore are also eaten. Along coasts, invertebrates and carrion (e.g., seals and sea lions) probably form a greater part of the diet of young birds. On Kamchatka, prior to the arrival of salmon, ducks and gulls may constitute 50-70% of the food fed to nestlings. After spawning, salmon returning to the sea may also provide an important food source up to the onset of winter. Eagles overwintering in Kamchatka take hares, ermine, sable, and fox (sometimes from the traps of commercial hunters). During winter, H. albicilla and golden eagles (Aquila chrysaetos) may also occur in feeding groups. On Hokkaido, eagles are attracted by abundant cod which peak in the Rausu Sea and Nemuro Straits in February. This resource supports an important commercial fishery which in turn helps to support eagles. In February, the commercial catch can reach 1,250 tons offish daily. If only 0.5% of the catch escapes or slips into the water, enough food becomes available to feed thousands more eagles than are gathered.
Video Stellers Sea Eagle
copyright: Eugene Potapov
In Russia, it is threatened by habitat alteration during the development of hydroelectric power projects, proposed large-scale coastal and offshore developments for the petrochemical industry, and logging for timber. Industrial pollution of rivers and high levels of DDT/DDE and PCBs are further threats. Over-fishing has caused a decline of fish stocks in Russia and Japan which has led to an increasing tendency of birds on Hokkaido to move inland and scavenge on sika deer carcasses left by hunters, exposing them to a risk of lead poisoning through ingestion of lead shot