Steller's sea eagle

Name and taxonomy

Peter Simon Pallas described the bird in 1811 as Aquila pelagica. The species name comes from the Greek word for the open sea. Coenraad Jacob Temminck renamed it the white-winged eagle in 1824. In 1832 Heinrich von Kittlitz gave it the name Falco imperator. George Robert Gray placed it in the genus Haliaeetus in 1849. The International Ornithologists' Union settled on the English name Steller's sea eagle.

The name honours Georg Wilhelm Steller, a German naturalist who lived from 1709 to 1746. He sailed with Vitus Bering on the second Kamchatka expedition. A jay, an eider, a sea lion and the extinct sea cow all carry his name too. Russian speakers call the bird the white-shouldered sea eagle. In Japanese it is o-washi, the great eagle, and in Mandarin the tiger-headed sea eagle. The Korean name chamsuri means true eagle.

Evolution and relatives

The species belongs to Haliaeetus, the sea and fish eagles. It is the largest bird in that genus. A study of mitochondrial DNA in 1996 dated its split from its nearest kin. It parted from the line of the bald eagle and the white-tailed eagle three to four million years ago. Those three share yellow eyes, bills and talons, which Pallas's fish eagle lacks. Its size and its narrow range suggest a relict of the ice ages.

No subspecies are accepted. A dark form without white on the wings was once named as one. That bird was last seen in the wild in 1968 and was thought to be gone. A dark female then hatched in a German breeding centre in 2001. Both her parents wore normal plumage, which showed the dark form to be a rare colour morph. One of her sons, hatched in 2014, is dark as well.

Appearance

The adult is dark brown or black over most of the body. White marks the shoulders, the thighs, the under-tail and the leading edge of the wing. The tail is white and shaped like a diamond. It carries 14 tail feathers, where other sea eagles carry 12. The body measures 85 to 105 cm, and males average about 89 cm against 100 cm for females. The wingspan runs 195 to 250 cm, with a median near 2.13 metres.

The bill is enormous and probably the largest of any living eagle. The skull measures about 14.6 cm and the upper bill 62 to 75 millimetres. The legs and tail are short for such a big eagle. The toes are short and stout, and the talons are short and strongly curved. Rough bumps called spicules cover the sole of each foot and grip a wet fish. One veterinarian was badly hurt when a female drove her talons through his arm.

A newly hatched chick wears silky white down that soon turns smoky grey-brown. A juvenile is a uniform sooty brown, with a white tail mottled in black. Its eyes are dark brown, its legs whitish and its bill blackish. The bird passes through at least three intermediate plumages. Full adult colours appear in the fourth or fifth year. Even a young bird has a yellow bill, which no other sea eagle shows.

Habitat and range

The eagle breeds on the Kamchatka Peninsula and around the Sea of Okhotsk. It also nests on the lower Amur River, on northern Sakhalin and on the Shantar Islands. Nests sit on rocky outcrops or in tall trees by the coast or a large river. The birds favour stands of Erman's birch and floodplain forest of larch, alder, willow and poplar. They keep close to sea level, and inland records are rare. GBIF holds occurrence records from 22 countries and territories.

Winter drives many birds south. Drifting ice on the Sea of Okhotsk pushes thousands towards Japan every year. The ice reaches Hokkaido in late January, and eagle numbers in the Nemuro Strait peak in late February. Birds gather on the coast and on lakes near it, beside many white-tailed eagles. They leave between late March and late April, with the adults going first. Coastal nesters may skip the journey altogether when the water stays open.

The species wanders less than the white-tailed eagle does. Even so, stray birds have reached the Aleutians, the Pribilofs and Kodiak Island. One bird has toured North America since August 2020, when it appeared near Denali. It then turned up in Texas, in Atlantic Canada, in Massachusetts and along the coast of Maine. Wing marks show that every sighting belongs to the same eagle. Birders nicknamed it Stella, and their travel gave a lift to local businesses.

Diet and hunting

The eagle sits at the top of its food web and lives mainly on fish. Pink salmon and chum salmon are the favourites on the rivers. Grayling and three-spined stickleback fill in when salmon are scarce. A mature pink salmon averages about 2.2 kilograms and a chum about 5 kg. The eagle often takes fish of 6 to 7 kg. Along the coast it also takes wolffish, lumpfish and sculpins.

On the Amur, fish supply roughly 80% of what the eagles eat. Elsewhere other prey makes up nearly half of it. Seabirds are the second staple, above all murres, kittiwakes and slaty-backed gulls. Ducks, geese, swans, cranes and herons all appear in the diet. Grouse and ptarmigan matter in Russia, and no other sea eagle takes them often. The bird also kills sables, minks, foxes, voles, hares and small dogs.

Most hunting happens from a perch 5 to 30 metres above the water. The eagle may also circle 6 to 7 m up and drop onto its prey. Sometimes it simply stands on a sandbank or an ice floe and grabs a passing fish. Carrion matters in winter, and it will strip a seal or a sea lion where it lies. About 35% of the birds wintering in Japan move inland to feed on dead sika deer. One study estimated that seal pups carried away in flight weighed at least 9.1 kg.

Behaviour and social life

The eagle is active by day and usually alone. Rich food brings it together in numbers all the same. Spawning rivers draw crowds from August into September. Gatherings of as many as 700 birds have been reported on Kamchatka. Outside the breeding season the birds probably roost together near their feeding grounds. Migrants travel singly, and a loose group keeps 100 to 200 m apart.

Where eagles feed in a group, food theft is common. Adults gain most from it, though young birds try it just as often. The bold black and white pattern may help the birds sort out rank at a carcass. The species is described as more aggressive and more active than its two close relatives. It robs ospreys where the two overlap. One bird was filmed chasing and robbing a cinereous vulture, the largest of all accipitrids.

Size does not settle every contest. A golden eagle has been filmed pushing a young Steller's off its fish. Smaller eagles sometimes take a fish from a distracted bird face to face. At other times three eagle species feed side by side and ignore each other. Competition turns fierce inland, where food and nest sites are both scarce. On these rivers golden eagles depend on fish, which happens nowhere else in their range.

Communication and senses

The usual call is a deep barking cry, written as ra-ra-ra-raurau. The bird also gives honking notes that recall a Canada goose. An angry bird sounds like a white-tailed eagle but deeper. During the courtship display a pair calls like very loud, deep-voiced gulls. The display itself is a soaring flight above the nesting ground.

Sight probably does most of the work for a fish-hunting raptor. The eagle spots a fish from a perch tens of metres up and dives on it. It also reads other eagles, and it tells a familiar person from a stranger. Birds on Hokkaido walk within a few feet of fishermen they know. They keep their distance when a stranger stands on the same ice. The plumage pattern may itself carry a signal to other eagles.

Reproduction and life cycle

The breeding season runs from February through August. Nest building starts in February or March, and the display flights follow in March. A pair keeps two to four nests in one territory and uses them in turn. A nest is a bulky pile of sticks up to 1.5 metres deep and 2.5 m across. It sits 15 to 20 m up a tree or on a rock, and sometimes as high as 45 m. Alternate nests usually stand within 900 m of each other.

Pairs were long thought to stay together for life. Genetic work found chicks that closely resemble chicks from other nests. That result may point to occasional mating outside the pair. The greenish-white eggs arrive in April or May. Each egg measures about 78 to 85 mm long and weighs around 160 grams. A clutch holds one to three eggs, and two is the average.

Incubation lasts about 39 to 45 days. The chicks hatch helpless and covered in white down. Parents bring two or three live fish of 20 to 30 cm to the nest each day. The young fly in August or early September, about 70 days after hatching. Usually only one chick reaches adulthood, though three may fledge. Both parents feed the brood to independence.

Only 45 to 67% of eggs produce a grown bird. Egg theft and collapsed nests cause most of the loss, and up to 25% of nestlings die. Adult plumage arrives at four years of age. First breeding waits another year or two, at six or seven years old. No one has measured the lifespan directly. ADW puts it near the white-tailed eagle's 20 to 25 years in the wild.

Predators and threats

A grown Steller's sea eagle has no natural predator. Eggs and small chicks are another matter. Sables, ermines and crows raid a nest by stealth when the parents are away. A parent kills any of them that it catches. One brown bear climbed to a nest set on rock and ate the eaglet, which is rare. A grown chick in a tree nest is probably safe from everything.

The dangers that count are all human. Logging and coastal development take away the tall trees the birds nest in. Industrial pollution reaches the rivers and the sea. Overfishing strips the salmon that the nestlings depend on. Heavy flooding in Russian rivers has caused near total nest failure in some years. Trappers still shoot eagles that steal fur-bearing animals from their traps.

Lead is the newest threat. Eagles on Hokkaido move inland to feed on deer carcasses left by hunters. The meat holds lead shot, which poisons a bird that swallows it. Poisoned birds lose weight sharply before they die. Climate change probably drives both the floods and the loss of drift ice.

Population and conservation

The IUCN Red List places Steller's sea eagle in the Vulnerable category. The total stands at about 5,000 birds and is falling. Counts add up to roughly 3,200 breeding pairs. Kamchatka holds about 4,000 eagles, with 320 pairs recorded and 89 nesting areas unmonitored. Over 1,200 pairs breed in the Koryak mountains and along the Bay of Penshina. iNaturalist holds 1,844 observations of the species.

Another 600 pairs nest on the lower Amur and about 280 on Sakhalin. The Khabarovsk coast holds about 500 pairs and the Shantar Islands about 100. Up to 3,500 birds may winter on Kamchatka and roughly 2,000 on Hokkaido. Russia lists the eagle in its Red Book. Japan protects it as a national treasure, and Korea and China protect it too. It sits on Appendix II of CITES, which controls international trade.

Most Russian breeding sites lie inside nature reserves. Japan has set aside key wintering habitat as well. The food supply in the main wintering areas remains secure for now. Commercial cod fishing off Rausu even helps to feed the birds. The outlook is therefore called favourable, despite the falling count.

Relationship with humans

The eagle and the fishing industry live off the same fish. Pacific cod peak off Rausu and in the Nemuro Strait in February. That fishery supports both a fleet and the wintering eagles. Alaska pollock and cod are the main winter foods in Japan. Eagles walk close to fishermen they recognise and keep away from strangers.

Not every meeting is friendly. Russian trappers lose fur-bearing animals to eagles and shoot the birds in return. Immature eagles hang about slaughterhouses in winter to snatch offal. Hunters who leave a shot deer behind poison the eagles that feed on it. Lead-free ammunition would probably remove that risk.

Watching the eagles has become an industry of its own. Boats carry visitors onto the drift ice off Hokkaido each February. The wandering bird known as Stella drew birders across North America. Their spending lifted local businesses in Maine and Newfoundland. That bird began to show nesting behaviour in Newfoundland in 2024. It has driven off bald eagles nesting nearby.

In culture and myth

In Japan the bird is o-washi, the great eagle, and it is protected as a national treasure. Japanese law grants that status to animals of high scientific value under the Cultural Properties system. Winter eagle watching on the ice off Hokkaido has become a fixture of Japanese wildlife photography. In Korean tradition the bird is chamsuri, which means the true eagle. In Mandarin it is the tiger-headed sea eagle, after the size and colour of its head.

The English name carries a piece of exploration history. Georg Wilhelm Steller joined Vitus Bering's voyage from Kamchatka in the 1740s. He described six birds and mammals new to European science on that journey. Two of the six are now extinct, including the sea cow that also bears his name. Three more, this eagle among them, are near threatened or vulnerable.

Modern birding has made a celebrity of one individual. Stella has been tracked across the continent since 2020 by wing markings. Crowds gathered on the Taunton River in Massachusetts and along the Maine coast to see her. The bird settled in Newfoundland and now stays there all year. Her story appears to have done more for the species' fame than any other event.