Steller's Sea-Eagle

BirdEast Asia

Oct 27

Haliaeetus pelagicus

Steller's sea-eagle is a rare raptor from the rocky coasts and rivers of northeastern Siberia — flying southwards to Hokkaido, Japan, in winter. It's the world's heaviest eagle and a particularly aggressive species, known to frequently steal fish caught by other eagles.

Glacial Relic

Siberia is often synonymous with glacial subzero temperatures and harsh untamed wilderness, where only the toughest survive. Vast taiga forests give way to treeless tundras and near-inhospitable permafrost. Imposing mountain ranges snake their way through eastern Siberia, terminating in the Kolyma and Koryak mountains in the northeast — one of the least populated regions on Earth. The mountains dispel their frigid runoff as streams which congregate in rivers, and empty into the often ice-laden Sea of Okhotsk or the Bering Sea.

Above these pristine rivers and isolated rocky coasts soars a magnificent predator. It's held aloft on immense wings — stretching to an average span of 1.3 metres (4.2 ft), with the largest known individuals possessing wingspans of 2.5 metres (over 8 ft). Its feathers are rich-brown, interrupted by light patches on its shoulders, belly, and tail — white like spotless snow. It opens its bright-yellow beak, which is curved down into an intimidating hooked tip, and utters a deep bark-like cry; ra-ra-ra-raurau! This feathered giant is believed to be a "glacial relic", evolving on the narrow coast of northeastern Asia over the waxing and waning of multiple Ice Ages. Today, this ancient raptor is known as Steller's sea-eagle.

As it flies, its striking yellow feet remain nestled beneath its immaculately white wedge-shaped tail. The underside of each foot is textured with ridged spicules — bard-like structures that assist with grip — and is equipped with four black talons; long and razor-sharp. It searches the tumultuous waters below with its golden eyes. Its binocular vision, with both eyes at the front of its head, allows it to precisely pinpoint its meal; usually large fish, such as salmon or trout. It hunts during the day, circling 6 to 7 metres (~20 - 23 ft) above the water or, alternatively, it sits watching from a perch that can be as tall as 30 metres (~100 ft). Once it spots its target, it sweeps down, clawed feet extending forward. The sea-eagle's rough-skinned feet snag against its prey's wet and slippery scales, while its talons pierce the flesh, clutching firmly until the wriggling victim is dead. This eagle's strong grip, vast wings, and great size — one of the largest eagles in the world — enables it to haul up prey weighing up to 7 kg (15 lbs).

Aquiline Piracy

The most bountiful time of year for the Steller's sea-eagle is during the salmon run. Although typically solitary birds, these eagles have been known to amass in large numbers — some reports estimating up to 700 — during the surges of salmon that migrate annually to their freshwater breeding grounds. Rather than searching and diving, the sea-eagles may stand in shallow water or on nearby ice and snatch fish as they stream by. But why hunt at all if you can let someone else do the hard work? During times of abundant prey, adult Steller's sea-eagles will often harass and bully smaller eagles into giving up their catches — stealing from other Steller's sea-eagles and eagles of different species, such as white-tailed eagles (although the odds don't always favour the sea-eagle) — a behaviour known as kleptoparasitism.

Such piracy is common among eagles, and raptors in general. While the Steller's steals from the white-tailed eagle, one needn't feel too sorry, for, throughout its wide range, the white-tailed is known to opportunistically snatch meals from other birds of prey and even from otters — nicknamed the "lazy bird" by some, for its reluctance to do its own hunting. Red-tailed hawks and peregrine falcons — known for diving at prey at neck-breaking speeds — are also accomplished thieves, often pestering other hawks on the ground for their food. The golden eagle, in turn, will pirate on the red-tails, as well as on the iconically majestic bald eagle — who, in an unexpected subversion of character, is a chronic kleptomaniac, known to frequently steal fish from ospreys by attacking them mid-flight so as to make them drop their catch. The world of eagles, hawks, and falcons is a complicated web of harassment and thievery. There appears to be little honour among raptors.

Lofty Fortresses

On the Kamchatka Peninsula — a 1,250-kilometre-long (777 mi) bit of land in the Russian Far East, straddled by the Sea of Okhotsk and the Pacific Ocean — the average daily temperature in February is a bitter -16°C (3°F), reaching an annual high in July, with a daily average temperature of almost 20°C (68°F). As the days go from deathly cold to pleasantly warm between the months of February through August, Steller's sea-eagles abandon their solitary lifestyles to conceive and raise families. For young eagles, courtship may begin while the lands are still frozen and snow-laden. Soaring at lofty heights, their calls echo across the landscape; less cawing eagle and more yelping seagull. Older eagles often reunite with their partners from previous years, even returning to their old nests. These tree-top fortresses — built up to 30 metres (100 ft) off the ground in the crowns of dead or open-topped trees, sometimes made up of more than 400 large branches and reaching sizes of up to two meters (6.6 ft) across and two to four meters (6.6 - 13 ft) thick — are known as aeries.

A sea-eagle pair returning to last year's aerie will often touch it up by making some adjustments and repairing any damage, before laying a clutch of 1 to 3 greenish-white eggs, usually in the middle of spring. After around 38 days of incubation, the fluffy white chicks hatch into a spring (or summer) world of plenty and a meal of fish from their parents. By the time the eaglets reach 5 weeks of age, they're consuming about 0.4 kg (1 pound) of fish every day, dutifully caught and brought by their parents from a nearby river. At 10 weeks the young learn to fly and achieve independence shortly after.

But not everything always goes so smoothly. In an aerie of up to three chicks, usually only one survives to fly free. While the massive adults have little to fear from predators, their eggs and chicks are vulnerable to dextrous mammals like martens, who'll deftly climb trees to sneak into a nest, or crafty opportunists like crows. Another danger is the aerie itself. Steller's sea-eagle aeries can sometimes weigh over a hundred kilograms (several hundred pounds), add to that the weight of the world's heaviest eagle — the larger females with an average mass of 9 kg (~20 lbs) — and the whole thing may come crashing down as the supporting branches snap beneath the burden.

Winter Holidays

As September plunges northeastern Russia into coldness once more, many Steller's sea-eagles begin their migration south to relatively warmer coasts. While Japan's northernmost island of Hokkaido is known for its heavy snowfalls — in the Aomori prefecture, just south of Hokkaido, blankets of snow five metres (16ft) thick have been recorded — compared to the Siberian winter, it is preferable. From October onwards, the migrating sea-eagles arrive in Japan, either making their way along the Sea of Okhotsk coast and crossing the Soya Strait, or flying over the Kuril Islands (some remaining there for the winter), crossing from one peninsula in Russia (Kamchatka) to another in Japan (Shiretoko) — Shiretoko National Park is a prime spot for spotting Steller's sea-eagles in Japan. Some migrants may continue on; flying further south into western Japan, northeastern China, Taiwan, and the Korean Peninsula. Far-wandering individuals — likely lost — have even been seen across the Pacific in the United States.

Raptorial Etymology

Clockwise from top left: Steller’s jay (*Cyanocitta stelleri*), Steller sea lion (*Eumetopias jubatus*), and the extinct Steller’s sea cow (*Hydrodamalis gigas*).

Steller's sea-eagle is known by many names throughout its range. In Russian, it is called the "белоплечий орлан" (white-shouldered eagle), the "тихоокеа́нский орлан" (Pacific eagle), or just the "морской орел" (sea eagle). In Korean it is the chamsuri (참수리), or the "true eagle". In Chinese it is the hǔtóu hǎidiāo (虎頭海鵰), or the "tiger-headed sea eagle". And in Japan, it's known as the ō-washi (オオワシ), the "large/great eagle".

But, who is this Steller, and why is this "his" sea-eagle? The name refers to one Georg Wilhelm Steller, a German naturalist born in 1709 — famous for discovering several new species of plants and animals. As such, he "owns" — lends his name to — a diverse menagerie of species beyond this sea-eagle. There is Steller's jay; an understated but beautiful blue and black crested bird from North America. The Steller sea lion; an inhabitant of the North Pacific Ocean and the largest of all sea lions. And Steller's sea cow; a gentle algae and sea grass grazer, that was tragically driven to extinction by intense over-hunting less than 30 years after its formal discovery.

From left to right; a white-tailed eagle (*Haliaeetus* *albicilla*), bald eagle (*H. leucocephalus*), and Pallas's fish eagle (*H. leucoryphus*).

Steller's sea-eagle's scientific name is Haliaeetus pelagicus. Its specific name stems from the Latin word for pelagic; "relating to, or living or occurring in the open sea". While this sea-eagle isn't truly pelagic — like albatrosses or storm petrels, who spend most of their lives flying over open ocean, only returning to land to breed — it does mostly live along the coast, rarely ranges far inland, and hunts at sea. It shares its genus name —Haliaeetus, New Latin for "sea eagle" — with three other piscivorous eagles. These are the far-ranging white-tailed eagle (H. albicilla), the thieving bald eagle (H. leucocephalus), and Pallas's fish eagle (H. leucoryphus), which, like Steller's, owes its title to a man who's lent his namesake to many species, including but not limited to; a squirrel, a legless lizard, a rosefinch, a gull, a now-extinct cormorant, a couple bats, and a grumpy cat. But, of the impressive Haliaeetus genus, Steller's sea-eagle is considered to be the most powerful and the most aggressive.

A Vulnerable Treasure

Power and aggression often do little when facing survival in a human-dominated world. In fact, they often have an antithetical effect on a species' longevity, as the now-extinct thylacine of Tasmania or the wolves of Britain and Japan can attest to. In Russia, the Steller's sea-eagle's sole breeding grounds, logging and the building of hydroelectric infrastructure are degrading and destroying its habitat while pollutants from local industries contaminate the rivers that it relies on for fish. There was a nightmarish case in 2006 when a flood of seabird carcasses (over 5,500 of them), slicked with petroleum oil washed up onto the shores of the Shiretoko Peninsula of Hokkaido. Opportunistic as they are, Steller's sea-eagles proceeded to feast on the carcasses, leading to two reported deaths from secondary oil poisoning. In much of Japan, there simply isn't enough fish to support a sizable population of these large birds. Overfishing has forced sea-eagles to rely more frequently on carrion — usually deer carcasses — often killed using lead shot, subsequently poisoning the eagles who eat it. This, at least, was remedied through a law banning lead shot, but only on the island of Hokkaido (with plans to outlaw lead shot nationally by 2030). But the scarcity of fish, as well as accidents such as collisions with cars and trains, and electrocutions from power lines, makes for a less than ideal habitat for the Steller's sea-eagle.

To protect a species effectively, we must first know about it — its full range, its habitat and food requirements, reproductive behaviour and life history, the status of its population and its members, genetic diversity — and the Steller's sea-eagle is a particularly difficult species to study, given its rugged and isolated habitat. The life history of the species, from fledging to maturation, is still quite cryptic and its lifespan isn't definitively known — only estimated based on related species to be around 20 to 25 years in the wild. Some research taking advantage of modern technology is on the way. Young sea-eagles are fitted with satellite leg tags to closely track their movements. But the research requires dedication, necessitating work in gruelling environments, where tagging a bird involves climbing a tree to reach nests as high as 30 metres (100 ft) off the ground, gently picking up an eaglet and placing it into a bag, climbing back down, recording its condition — measuring it, weighing it, and taking tissue samples — then climbing back up to return it to its nest.

Steller's sea-eagle is considered to be 'Vulnerable' as of its most recent 2021 assessment by the IUCN. Despite the species' legal protection in Russia, China, and South Korea, and Japan — where it is considered a "National Treasure" — the population is still decreasing, with recent counts estimating some 4,000 individuals remaining in the wild.

**Where Does It Live?**

⛰️ Along sea coasts and near large rivers with mature trees. Rarely seen far inland.
📍 Breeds in eastern Russia — the Sea of Okhotsk and the Kamchatka Peninsula. Winters on the Kuril Islands, Japan’s Hokkaido, and as far south as eastern China and Korea.

Size // Large
Wingspan // 2 – 2.5 m (6.6 – 8.2 ft)
Length // 86.5 – 105 cm (2.8 to 3.4 ft)
Weight // Up to 9 kg (20 lbs)
Activity: Diurnal ☀️
Lifestyle: Solitary/ Pair (during breeding season) 👤/ 👥
Lifespan: Likely around 20-25 years
Diet: Carnivore
Favorite Food: Fish 🐟
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Genus: Haliaeetus
Species: H. pelagicus

The average wingspan of a Steller's sea-eagle is 1.3 metres (4.2 ft), but the largest known individuals possess wingspans of 2.5 metres (over 8 ft). The heftier females have an average mass of 9 kg (~20 lbs).

It prefers to eat large fish such as salmon or trout — able to lift prey weighing up to 7 kg (15 lbs).

When food is more scarce, the sea-eagle turns to other sources; from crabs and mussels, to other birds like gulls and puffins, to small mammals, or scavenged carrion, such as deer carcasses.

In the winter, some sea-eagles are even known to approach fishermen, but only if they were previously acquainted.

It hunts during the day, circling 6 to 7 metres (~20 - 23 ft) above the water or, alternatively, it sits watching from a perch that can be as tall as 30 metres (~100 ft).

The underside of each of its yellow feet is textured with ridged spicules — bard-like structures that assist with grip, snagging against slippery prey.

Although these eagles are usually solitary, up to 700 have been seen gathered in one place during bountiful salmon runs.

During times of abundant prey, adult Steller's sea-eagles will often harass and bully smaller eagles into giving up their catches — they steal from other Steller's sea-eagles and eagles of different species, such as white-tailed eagles.

An eagle's nest is known as an aerie. A Steller's sea-eagle builds its aerie up to 30 metres (100 ft) off the ground in the crowns of dead or open-topped trees, sometimes made up of more than 400 large branches and reaching sizes of up to two meters (6.6 ft) across and two to four meters (6.6 - 13 ft) thick.

Sometimes, these treetop fortresses can become overloaded with weight; the supporting branches give away and the whole thing comes toppling to the ground.

Aeries are reused from year to year by returning eagle pairs, who'll lay a clutch of one to three eggs — however, only one chick usually survives to maturity.

While these eagles breed in northeastern Russia, come September, many Steller's sea-eagles begin their migrations southwards. Some settle on the Kuril Islands, others on Hokkaido, while others still fly further; to western Japan, northeastern China, Taiwan, and the Korean Peninsula. Far-wandering individuals — likely lost — have even been seen in the United States.

This species is named for Georg Wilhelm Steller, a German naturalist born in 1709. Steller has also given his namesake to a jay, a sea lion, and an extinct sea cow.

Steller's sea-eagle is considered to be 'vulnerable' as of its most recent 2021 assessment by the IUCN. The population is decreasing, with recent counts estimating some 4,000 individuals remaining in the wild.