Steller's Sea Eagle
Haliaeetus pelagicus
VULNERABLE
Hokkaido, Japan
The Steller’s Sea Eagle is one of the most remarkable birds I have seen against a backdrop of extreme landscapes exposed to incredibly harsh climate during the winter. Though familiar in summer to native peoples of the Russian Far East, of the Aleutian Islands and even south-west Alaska, and in winter to those in northern Japan, it was unknown to western ornithologists until the late 18th century.
Then, on Vitus Bering’s second journey to discover if Russia and North America were land-linked, it was described by the expedition’s German doctor/naturalist Georg Steller. Standing a metre tall, with a wingspan sometimes approaching 3 m and weighing as much as 9 kg, it is arguably among the largest eagles in the world (and certainly one of the biggest three or four).
The Steller’s is an immense eagle with a large head and a massive orange bill to match. The adults are striking, even from a great distance: a rich brown overall, with a snow-white tail, belly, and shoulder patches. The juvenile and immatures are darker but usually acquire a mostly white, wedge-shaped tail in the second year. The younger birds can be confused with young White-tailed Eagles, but the Steller’s is clearly distinguished by its larger bill, wedge-shaped tail, and unique wing shape, narrow at the tip, bulging in the middle, then narrowing near the body. They pluck fish from icy seas and follow fishing boats for scraps and are often associated with the White-tailed Eagles where prey is abundant.
It also has, without doubt, the most massive bill of any eagle. The eagle’s late discovery to western science was due to its remote range. Breeding eagles are confined to the Bering Sea coasts of southern Kamchatka and to northern and western coasts of the Sea of Okhotsk. In winter the eagles are largely confined to the southern Kuril Islands and Japan’s northern island of Hokkaido which is where I had the privilege of spending time with them on the drift ice.
Our journey to the ice began well before first light from Rausu-chō, a town located in Nemuro Subprefecture, Hokkaidō, Japan. We took an ice-breaker and ventured out into the drift ice. The word "Rausu" originates from the Ainu word Raushi, roughly meaning "Low-land" or "Place of men with beast-like spirit". It was about 16 or 20 degrees celsius below freezing and the wind chill bit through all the layers we had on. But once we saw the eagles - the Steller’s and the White-tailed - all was forgotten. In the two videos I have here the engines of the ice-breakers can be heard in the background trying to hold their ground in the moving and cracking ice.
‡‡‡‡‡
One of these eagles has become my logo and a couple more have been published. Click the button to view them.
In winter, climate and geography mean the Sea of Okhotsk defies its position (at about the same latitude as France’s Mediterranean coast) and freezes, Steller’s Sea Eagles wintering on or close to the sea ice, a curiosity that has attracted bird lovers and photographers for many years. Taking many years to mature, often producing only a single chick each year, and exposed to an incredibly harsh climate during the winter, the species was never abundant. There are estimated to be between 4,600 and 5,100 individuals, including 1,830-1,900 breeding pairs. The International Union for Conservation of Nature considers the Steller’s Sea-eagle “Vulnerable” due to moderate population decline caused primarily by habitat conversion in its breeding grounds, and from mortality caused by lead poisoning while overwintering in inland Japan. They are legally protected in Russia, Japan, China and South Korea.
The eagles now also have to contend with the exploration for fossil fuels in the Sea of Okhotsk, particularly on the island of Sakhalin (where the eagles additionally suffer predation by Brown Bears which climb their nesting trees to eat the nestlings). In recent years Russian researchers have worked hard, in conjunction with local oil companies, to reduce the threats from anthropogenic change and bear predation. However, the situation remains challenging, with evidence suggesting that throughout its range the Steller’s population is declining.
Steller’s Sea Eagle Range
These magnificent Steller's sea eagle are believed to breed only in far eastern Russia, along the coasts and surrounding islands of the Sea of Okhotsk and Bering Sea. Specifically 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 south of their breeding range, in the southern Kuril Islands, Russia and Hokkaidō, Japan. The Steller's sea eagle is less prone to vagrancy than the white-tailed eagle, as it lacks the long-range dispersal typical of juveniles of that species, but vagrant eagles have been found in North America, at locations including the Pribilof Islands and Kodiak Island, and inland in Asia to as far as Beijing in China and Yakutsk in Russia's Sakha Republic, and south to as far as Taiwan.
Each winter, many Steller's sea eagles migrate from their breeding grounds to Japan, and a few reach Korea or even farther afield. Other individuals do not migrate, but simply move to open water as winter approaches. Open water provides these eagles with their main food sources along coastlines and lakes. In their breeding grounds, Steller's sea eagles subsist largely on salmon, and they both hunt and scavenge for this resource. Annual salmon runs provide an enormous bounty and Steller's sea eagle nests are typically located near coasts and rivers where these fish appear en masse, and the fish are taken alive or dead. They are also opportunistic and versatile as both scavengers and predators. A variety of birds and mammals are taken when primary prey species are scarce and seabirds are an important food source for certain populations and pairs.
These birds of prey hunt from a perch or from flight by diving and clutching prey in their talons. They also stand in shallow water or on the ice and grab passing fish when the opportunity arises. Like other eagles, Steller's also steal food from other birds. In Japan, Steller's sea eagles feast on cod. In addition to fish, they eat crabs, shellfish, squid, small animals, ducks, gulls, and carrion. Seldom seen far from water, the Steller’s Sea-eagle is typically found along coastlines and coastal lagoons as well as inland on large lakes and in forested river valleys (mostly on lower stretches) up to an elevation of 1,000 meters. They require tall trees or high cliffs for nesting. During winter, eagles that remain in Russia typically forage along the coast and those rivers that remain open. Eagles that overwinter in Japan stay near fresh water or move into mountainous regions to feed on deer carcasses.
Steller's sea eagles do not occur in large numbers, but their populations appear to be stable. Their feathers were once highly prized, but today these magnificent birds are protected throughout their range. They are especially revered in Japan, where they are known as O-washi.
The large body size (see also Bergmann's rule) and distribution of Steller's sea eagle suggests it is a glacial relict, meaning it evolved in a narrow subarctic zone of the north-easternmost Asian coasts, which shifted its latitude according to ice age cycles, and never occurred anywhere else. Nests are built on large rocky outcroppings or at the tops of large trees on the coast and alongside large rivers with mature trees. Habitat with large Erman's birches (Betula ermanii) and floodplain forests of larches, alders, willows and poplar are preferred. Some eagles, especially those that nest in sea coast, may not migrate. 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, the eagles concentrate in coastal areas and on lakes near the coast, along with substantial numbers of white-tailed eagles. The 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.
This species is classified as vulnerable by the IUCN. They are legally protected, being classified as a National Treasure in Japan and mostly occurring in protected areas in Russia. However, many threats to their survival persist. These mainly include habitat alteration, industrial pollution, and overfishing, which in turn decrease their prey source. On the whole, the species' outlook is favorable. Outside the breeding range, food bases in the principal wintering areas are so far secure.
The first glimpse… far away over the mountains
The Steller's Sea Eagles on the drift ice off the coast of Rausu-chō, feeding in close proximity to our icebreaker.
For more videos: Video Shorts
Related Posts
