Birds: Steller's Sea-eagle

Range: northeastern Russian coast south to North Korea and Japan Habitat: tree-lined open river plains and rocky coastlines

Eagle of the sea

The Steller’s sea-eagle is dark, impressive, and the largest of all sea eagles. It is a diurnal, fish-eating raptor that mainly eats salmon and trout. Like its other close relatives—harriers, kites, and goshawks—it uses its excellent sense of vision to help it find its prey. Despite its large size and attractive appearance, the habits of the Steller's sea-eagle are not well known.

Big birds

The Steller’s sea-eagle is the heaviest known eagle, averaging 15 to 18 pounds (6.8 to 8 kilograms), and females can be 5 to 10 pounds (2 to 4 kilograms) larger than the males. Scientists believe that the eagles are "glacial relics" that evolved in the narrow subarctic zone of the northeast Asian coast and simply stayed there through multiple Ice Age cycles, never occurring anywhere else. Other northern sea eagles share the yellow legs, eyes, and beak of the Steller’s, and they are large birds as well, which seems to support this theory.

Hunting strategies

Steller’s sea-eagles spend much of their day perched up high, their eyes on the lookout for food. Like bald eagles and brown bears, the eagles take full advantage of the annual salmon run to gorge themselves on the spawning and dying fish. Steller’s sea-eagles are also known to hunt while flying and will take small mammals, fish, and seabirds by swooping down and catching them with their talons. These eagles have even been seen standing in shallow water or on the ice, grabbing fish as they swim by. Like other eagles, Steller’s will also steal food from other birds; this is known as kleptoparasitism.

I see you!

Like most other predators, Steller’s sea-eagles use binocular vision to precisely pinpoint the location of their lunch. Both eyes are set on the front of the bird’s head and focus on the same thing, providing depth perception. This is an important tool if you are diving more than 100 feet (30 meters) while trying to catch your food!

Airy aerie

Sea-eagle nests are called aeries, and they are built high in dead or open-topped trees near rivers or on rocky cliffs up to 100 feet (30 meters) above ground. These open sites give the birds easy access to and from their nests. Typically a pair will return to the same nest each year and add a little more to it to prepare for the season’s clutch, but pairs sometimes build and oversee more than one aerie and choose which one to use each spring. Aeries can be 6 to 8 feet (1.8 to 2.4 meters) wide and can weigh hundreds of pounds. It is not uncommon for the nests to grow so heavy that the branches they sit in will break and the nests come crashing to the ground.

Growing up slowly

Courtship occurs during late winter, and the females start laying greenish white eggs in mid-spring. One to three eggs are laid; usually only one chick survives, but two and even three babies have been raised successfully. Chicks are altricial, with downy gray feathers that gradually change to brown. The young learn to fly when they are about 10 weeks old. It takes about five years for young sea-eagles to reach sexual maturity and reach their striking adult plumage: dark bodies with bright white foreheads, shoulders, tails, and thighs.

A very rare raptor

The Steller’s sea-eagle may be one of the rarest raptors in the world. Very little is known about these birds of prey, due to the remote nature of their primary habitat. They breed 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 of Russia. They spend much of the warm season in this region, and some stay here year round. Many others migrate slightly southward for the winter to the southern Kuril Islands and to Hokkaido, Japan, where food is more plentiful. But that's it! This is the only region of the world where this species is found.

Eagles and humans

This vulnerable species is given complete legal protection in Russia, the only place it breeds, and in Japan, where it overwinters. In spite of these protections, human behavior continues to harm the remaining sea eagle population. In Russia, Steller’s are losing their habitat because of the development of hydroelectric power projects and logging in the forested areas where they nest. And the rivers where the eagles fish are being contaminated by chemicals from local industries. In Japan, sea-eagles eat both fish and carrion. Overfishing by humans in Japanese waters has lead the eagles to scavenge on sika deer remains left by hunters. Eating carrion filled with lead shot from the hunters has had devastating effects on the eagle population, leading to the outlawing of lead ammunition on Hokkaido. As of 2006, the world’s population was estimated at 5,000 birds, but it is slowly decreasing.

Still much to learn

Very little is known about these eagles, especially their early years. The San Diego Zoo and Natural Research, Ltd. are studying the movements of young Steller’s sea-eagles in their native habitat in hopes of protecting the species in the wild. Click here for more information and track the young eagles' migration! The San Diego Zoo also has a pair of Steller’s sea-eagles and has loaned pairs of birds to four other zoos in the United States. We hope that seeing these amazing raptors up close will encourage visitors to participate in the conservation of this rare species.