Classification and Range
Steller's sea-eagles belong to the family Accipitridae, a very diverse group of diurnal raptors encompassing eagles, hawks, kites, buzzards, harriers and New World Vultures. Eight fish eagles, including the bald eagle, make up the genus Haliaeetus. Its scientific name Haliaeetus pelagicus aptly describes the Steller's as "fish eagle of the open seas." Other names include white-shouldered eagle, Pacific eagle and O-washi, its name in Japan.
Steller's sea-eagles have a narrow coastal range in northeast Asia. They breed only in far eastern Russia on the Kamchatka peninsula, coastal areas around the Sea of Okhotsk and north along the West Bering Sea. Some remain year round, but the majority over-winter farther south in Hokkaido, Japan's northern main island, and on islands or coastal areas around the Sea of Okhotsk. Some migrate farther afield to the Korean peninsula and China, and a few vagrants roam as far as the Aleutian and Pribilof Islands in Alaska.
Their primary habitats include narrow coastal strips, islands, and forested valleys near lakes and river estuaries. High rocky cliffs along sea coasts and tall trees provide suitable nest sites. Steller's sea-eagles fish from the sea and near mouths of rivers where salmon spawn. These eagles share their limited habitat with the smaller white-tailed sea-eagle and the golden eagle.
Steller's sea-eagles are huge birds. They, along with the Harpy and Philippine eagles, have the distinction of being the largest and heaviest eagles. The smaller males weigh 11-13 pounds (4.9-6 kg) and the females weigh 15-20 pounds (6.8-9 kg). The body length ranges from 34-41 inches (85-105 cm) and the wingspan runs 6-8 feet (1.8-2.45 m). In comparison, the bald eagle weighs 8-14 pounds (3.6-6.3 kg).
Steller's sea-eagles possess distinctive physical characteristics for easy identification of adult birds. White feathers comprise large shoulder patches, long leggings, wedge-shaped tail, and small forehead and crown patches on a large blackish-brown body. Its immense and strong beak is deep, arched and yellow. Eyes, cere and feet are also yellow. Their unfeathered feet have powerful, curved talons and rough pads for grasping slippery fish and other prey. Immature birds have dark brown and lighter mottled feathers, dark brown eyes and orange beaks. They gradually acquire adult plumage and coloration in 4 to 5 years. A dark morph without the distinctive white shoulder markings also occurs, but is very rare.
Unknown but may live more than 20 years in the wild.
In the Wild: Primarily fish, especially salmon, trout and cod; sea birds, such as murres, gulls, auklet and cormorant; mammals, such as red fox, muskrat and seal; carrion.
Some of their food choices vary seasonally. In the spring birds will often steal carrion from traps. On Kamchatka, breeding pairs eat mainly salmon, while in northern Okhotsk Sea region, pairs in coastal areas sometimes focus on nesting sea birds while pairs in river areas concentrate on fish.
At the zoo: Rodents, rabbits, trout and quail
Reproduction - It's tough to raise a family!
Courtship occurs in March, but it is still winter on Kamchatka where average high temperature remains below freezing. Nests perch high on rocky cliffs or near tops of tall mature trees often in a dead area. Pairs add sticks to an existing nest which may reach 5 feet in height and 8 feet across. One to three white-green eggs are laid in April or May when highs reach slightly above freezing. Incubation length is uncertain, perhaps as long as 38 to 45 days. Usually only a single chick survives within a clutch, but often none survive and the adults abandon reproduction for that year.
Life Cycle - It's tough out there!
Success is far from assured even if a chick survives. Growing from a tiny altricial hatchling to a new fledgling takes about 10 weeks. Dangers include disease, predation from sable and vermin, and falls from - or with - the nest. Nests of great weight commonly collapse. The adult pair must protect the nest, as well as provide increasing amounts of food for the growing eaglet. By 10 weeks the young learn to fly, and by late summer they leave the nest, many to migrate southward to over-wintering areas. Many young eagles do not survive their first year on their own, succumbing to both natural and human-related causes. Not much is known about juveniles during the 4 to 5 years it takes to reach sexual maturity.
Steller's sea-eagles use varied techniques to obtain fish. Excellent vision, perhaps 6-8 times sharper than humans, enable eagles to spot prey from a distance. They perch high in trees or on cliffs then dive down to snatch fish near the water's surface. Less frequently they hunt on the wing, or by standing and grabbing passing fish. Eagles gather in large numbers where salmon spawn and take live fish and scavenge on the carcasses. Many sea-eagles, especially juveniles, find food through kleptoparasitism – stealing food from other birds. They take fish from eagles (other Steller's, white-tailed, golden) and other birds especially osprey. Dumps of offal from commercial fishing may also be utilized as a food source.
Birds and mammals also form part of the Steller's diet. Predation on ducks, gulls and nesting sea bird colonies provides a critical part of eaglet diets in some areas. Eagles hunt small mammals, such as hare and fox, but they also raid commercial traps for sable, mink and ermine. They will eat carrion of washed up seal and sea-lion carcasses. In the mid-1990's when cod runs crashed on Hokkaido, over-wintering Steller's ate from Sika deer carcasses left behind by hunters. Even tiny amounts of ingested lead fragments killed many birds.
Survival - Brrrr - Anyone know we're here?
Relatively little is known about the species. Its formidable and isolated habitat makes research difficult. In their summer breeding grounds, high temperatures average 52-63 degrees Fahrenheit (11-17 C). Winters are extremely severe with frozen seas and lakes, and drifting sea ice. Over-wintering areas in Hokkaido and on Kamchatka have average January highs of only 19°-21° (-6 to -7° C) with lows of 1°-8° F (-17° to -13° C.
Location at the Zoo
A Steller's sea-eagle resides in the award-winning Northern Trail. Look up in the trees to find its large stick nest. Visitors can often see wild bald eagles nesting in the elk yard from the Elk Overlook or near the gray wolf exhibit. Northern Trail also exhibits snowy and barred owls. The Raptor Center exhibits several raptor species, turkey vulture, ferruginous hawk, peregrine falcon, Harris' hawk, great-horned owl, spectacled owl and barn owl. Great gray owls reside in the Temperate Forest exhibit adjacent to Bug World.
Steller's sea-eagles are currently a CITES II species with an IUCN status of "Vulnerable" which is only one level below "Endangered." With no natural predators, human activities create its gravest threats. Trappers retaliate for losses of fur bearing animals. Poaching occurs. Habitat degradation results from industrial pollution, logging, hydroelectric projects, atmospheric pollution and over-fishing. Projected oil and gas drilling, pipelines and transport projects would further encroach on vital breeding and feeding habitat. Their range is already very limited and the eagles depend on clean waters and old forests.
The estimated population of 5,000 Steller's sea-eagles in the wild is small and declining. Since 2006 migration patterns of some nestlings have been tracked by satellite in-situ by the Zoological Society of San Diego, and Natural Research Ltd. biologists. Russian, Japanese and American conservation, educational and governmental institutions combine efforts within the International Working Group for the Steller's Eagle Conservation. These recent studies add to knowledge of the bird's breeding habits, population dynamics, and diet.
Conservation actions promote a future for Steller's sea-eagles. Russia and Japan give the species complete legal protection. The Steller's is a Natural Monument in Japan and the government banned the use of lead ammunition in Hokkaido. Very few zoos in America exhibit this species. San Diego Zoo has a pair and has loaned an additional four pairs to other zoos. Woodland Park Zoo acquired a potential breeding pair in 2010. With a proven history of exhibiting and breeding birds-of-prey, the zoo joins the conservation effort to save the magnificent Steller's sea-eagle.
We need raptors. Here are only a few of the benefits raptors provide:
Raptors help keep animal populations in balance.
Raptors consume many animals that humans consider as pests, including mice, rats and destructive species of insects. This helps to control disease and damage to crops.
As top predators of their food chain, raptors are an indicator species of the overall health of the ecosystem in which they live.
Of equal importance, witnessing wild raptors enriches each of our lives. Imagine what life would be like if we could no longer see a raptor soaring through the sky.
Woodland Park Zoo is Helping - With Your Support!
Woodland Park Zoo once rehabilitated injured and sick eagles. The zoo cared for more than 200 bald and golden eagles, peregrine falcons and other birds of prey. The zoo returned more than 70 eagles to the wild in the Pacific Northwest. Sometimes, due to injuries, certain birds could not be released. These were sent to wildlife facilities where they were used to educate people about birds of prey.
How You Can Help!
Efforts to save threatened and endangered raptors require cooperation and support at international, national, regional and individual levels. You can help in this cause. Join and become active in Woodland Park Zoo and other conservation organizations of your choice.
Contact Woodland Park Zoo at firstname.lastname@example.org to find out how you can support conservation efforts at the zoo. Learn other ways you can help conserve wildlife and the habitats they require for survival by visiting our How You Can Help page.
Sources and Suggested Reading
"Birds: Steller's Sea-Eagle." http://www.sandiegozoo.org/animalbytes/t-stellers_sea_eagle.html
"Species Sunopsis Steller's Sea-Eagle." http://www.fadr.msu.ru/fadr_e/index_e.html
"Steller's Sea-Eagle." http://www.birdforum.net
Steller's Sea-Eagle Conservation
"Steller's Sea-eagle Haliaeetus pelagicus." http://www.birdlife.org/datazone/speciesfactsheet.php?id=3366
Thiollay, J.M. "Family ACCIPITIDAE (Hawks and Eagles)." del Hoyo, Josep and Andrew Elliot, Jordi Saragatal. Handbook of the Birds of the World, volume 2. Lynx Edicions, Barcelona, 1994.
Weidensaul, Scott. Raptors: the Birds of Prey. Lyons and Burford, Publishers, NY, NY, 1996.
Williams, Laura. "The Secret Lives of Sea-Eagles." National Wildlife.
Utekhina, Irina and Eugene Potapov and Michael J McGrady. "Diet of the Steller's Sea Eagle in the Northern Sea of Okhotsk."