STELLER'S SEA EAGLES: CHARACTERISTICS, BEHAVIOR AND REPRODUCTION

STELLER'S SEA EAGLE

Steller's sea eagle

Steller's sea eagles (Haliaeetus pelagicus) are among one the world's most spectacular-looking birds. Black, except for white stripes on their tail legs and wings, they are slightly larger than American bald eagles, with a wingspan of up three meters, a body length of one meter, and weighing between 5.5 and 9 kilograms. They often look bigger because they tend to fluff up their feathers for better insulation.

Inhabiting the frigid coastal waters off of eastern Russia and Hokkaido, Japan, Steller's sea eagles gather in the winter at Nemuro Channel to feast on small fish known as o-washi in Japan, sometimes resting on platforms of sea ice. About 6,000 to 7,000 Stellers' Sea Eagles remain, with about 2,000 gathering to feed off the northeast coast Hokkaido in the winter. Many follow fishing boats or gather in the morning near fishermen to collect leftovers.

Steller's sea eagles are named after George Steller, a German naturalist who explored the Kamchatka Peninsula in the 1740s. The eagles have been carefully studied by Russian biologist Alexander Ladygin. Little is known about their lifespan, but it is thought to be similar to that of white-tailed sea eagles (Haliaeetus albicilla), their close relatives, which live 20 to 25 years in the wild.

Bird Guidebooks “Guide to the Birds of China” by John MacKinnon (Oxford University Press), “A field Guide to the Birds of Russia and Adjacent Territories” by V.E. Flint (Princeton University Press)and a “Birdwatchers's Guide to Japan” by Mark Brazil (Kodansha). Birding Websites: Birds of Japan Gallery by Monte Taylor Birds of Japan ; Birding Hotspots JapanBirding Hotspots Birdwatching in Japan Birding Pal; Steller's Sea Eagle National Geographic animals.nationalgeographic.com ;Bird Life International birdlife.org

Steller’s Sea Eagle Habitat, Migrations and Where They Are Found

Steller's sea eagles nest in eastern Russia and mainly found there along the Sea of Okhotsk, on the Kamchatka Peninsula, as far south as lower reaches of the Amur River, and on northern Sakhalin and the Shantar Islands. During the winter many migrate south to the islands and sea ice north of Hokkaido, Japan. They migrate as far south as eastern China and Korea. Vagrant individuals have also been spotted in Taiwan, Canada and the United States. [Source: Danielle Nelson, Animal Diversity Web (ADW), Wikipedia]

Steller's sea eagle range : orange: breeding only; green: resident all year; dark blue: winter only; light blue: vagrant range

Steller's sea eagles nest along sea coasts or near large rivers with mature trees. They prefer sea coasts that are dotted with estuaries and river mouths and are rarely seen very inland. They nest on large, rocky outcroppings or at the tops of large trees and can be seen in rivers, coastal areas, estuaries, wetlands such as marshes and swamps and areas adjacent to rivers and other water bodies. Migrating Steller's sea eagles winter along rivers in Japan or on sea ice off the coast and occasionally move to mountainous inland areas. They are found in other places in northern waters with sea ice for them to perch on.

Some eagles, especially those that nest on seacoasts, may not migrate. The timing, duration, and extent of migration depends on ice conditions and food availability. Those that stay on Kamchatka ride out the winter in forests and river valleys near the coast. They appear to be residential adults.

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, eagles concentrate in coastal areas and on lakes near the coast, along with large numbers of white-tailed eagles. Steller's sea eagles start heading north between late March and late April, with adults typically leaving before juveniles. Migrants tend to follow seacoasts and are usually observed flying alone.

Steller’s Sea Eagle Characteristics

Steller's sea eagles are largest eagles in the world in terms of weight. They are the largest bird in the genus Haliaeetus — which includes bald eagles, white-tailed eagles and Pallas’s fish eagles — and are among the world’s largest raptors. Other large eagles including the harpy eagle, found in Central and South America, which weighs up to 9.1 kilograms (20 pounds), about the same as a Steller's sea eagle, and has a wingspan of up to two meters (6 feet, 6 inches). The Philippine eagle has a body length of up to 0.9 meters (3 feet).

Steller's sea eagles weigh up to 9.5 kilograms (21 pounds) have a head and body length that ranges from 85 to 94 centimeters (33.5 to 37 inches). Their average wingspan is 118 centimeters (46.5 inches) for males and 136 centimeters (53.5 inches) for females. They are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them) and warm-blooded (homoiothermic, have a constant body temperature, usually higher than the temperature of their surroundings). Sexual Dimorphism (differences between males and females) is present: Females are larger than males. Average weight for males is six kilograms (13.2 pounds) for males and 9.5 kilograms (21 pounds) for females.[Source: Danielle Nelson, Animal Diversity Web (ADW) /=]

Steller's sea eagle head and large bill

Steller's sea eagles have dark brown to black feathers on the majority of their body and white on their shoulders, thighs, and crown. They have wedged-shaped, white tails, very large yellow beaks, and sharp, yellow talons. Steller's sea eaglets are black and fledge in 90 days. Their striking white shoulders, tail, legs and forehead do not develop for six to eight years.

All sea and fish eagles have relatively short and stout touts, with the bottom of the foot covered in spicules and the talons being relatively shorter and more strongly curved than in comparably- sized forest and field egales. Spicules are bumpy waves all along the bottom of their feet, which allow them to hold fish that may otherwise slip out of their grasp. Steller's sea eagle feet are very powerful despite not having talons as long as those on harpy eagles. Once a female grabbed the arm of a wildlife veterinarian so hard that the bird’s talons pierced through to the other side of his arm.

The Steller's sea eagles’s skull is around 14.6 centimeters (5.7 inches) long. The bill from the gape to the tip is around 1.17 centimeters (4.6 inches), making it probably the largest of any living eagle, just surpassing that of the Philippine eagle. Eagles have tongues with backward-facing barbs called "rear-directed papillae," which help them swallow prey, according to the Center for Conservation Biology, a research group at the College of William and Mary and the Virginia Commonwealth University. When eagle parents are feeding their young, they use their tongues to help keep away large bones, furry chunks and sharp fins that could cause the chicks to choke, according to the Raptor Resource Project, a nonprofit bird group based in Iowa. [Source Laura Geggel, Live Science, July 11, 2024]

Steller’s Sea Eagle Food and Eating Behavior

Steller’s sea eagle are primarily piscivores (eat fish) but are also recognized as carnivores (eat meat or animal parts) and can be scavenger. Animal foods include birds, mammals, fish carrion mollusks aquatic crustaceans. The main prey of Steller's sea eagles is salmon, taken either dead or alive, usually pink salmon or chum salmon. They also eat trout, grayling and three-spined stickleback. When salmon and fish are not not available, Steller’s sea eagle eat a range other foods, including crabs, mussels, gulls, small mammals and carrion. [Source: Danielle Nelson, Animal Diversity Web (ADW) /=\, Wikipedia]

Three types of hunting behaviors by Steller’s sea eagle have been documented: 1) hunting from a perch; 2) hunting on the wing while circling six to seven meters above the water; and 3) hunting in shallow water. When Steller’s sea eagles gather in the winter at Nemuro Channel to feast on Pacific cod and small fish known as o-washi in Japanese, sometimes resting on platforms of sea ice. Many follow fishing boats or gather in the morning near fishermen to collect leftovers.

Fish make up about 80 percent of the diet of eagles nesting in the Amur River In other places, other prey forms almost an equal amount of the diet. Along the sea coast and in Kamchatka, water birds such as ducks, geese, swans, cranes, herons, gulls and seabirds — particularly slaty-backed gulls, common and thick-billed murres black-legged kittiwakes, crested auklets and pelagic cormorants — are favored prey. Among the terrestrial mammalian carnivores taken as prey are sable, Arctic fox, red fox, small domestic dogs, northern red-backed voles and tundra voles. Carrion, especially that of mammals, is commonly eaten during the winter. Around 35 percent of eagles wintering in Japan move inland and feed largely on mammalian carcasses, predominantly those sika deer. Juvenile Steller's sea eagles may frequent slaughterhouses to pirate bits of offal. They been recorded preying occasionally on young seals.

Steller's Sea Eagle Gorging on Salmon at Lake Kuril at Kamchatka

Feeding Hundreds of Steller's sea eagles gather at Lake Kuril (Kurilskoye) on the Kamchatka Peninsula of eastern Russia in the winter. They spend most of their time perched in the trees and come to life during the winter sockeye salmon run, the largest in Asia. Steller's sea eagles sometimes have such difficulty finding in food in winter they starve but those that gather around Lake Kuril sometimes are so gorged with fish they can't fly and naturalist have caught them by hand. [Source: Klaus Nigge, National Geographic, March 1999]

Klaus Nigge wrote in National Geographic: “Steller's sea eagles eat like sibling rivals — they seldom dine alone, and few scraps of food are won without a squabble...Eagles begin each day watching for magpies and crows. Although equipped for hunting, eagles prefer to let other keen-eyed birds lead them to beached salmon. The scouts get food in return. An eagle's massive can tear open a fresh salmon's tough skin, allowing smaller birds to sneak a meal."

Kleptoparasitism (when an animal steals food from another animal) has often been observed when feeding occurs in groups and food is abundant. Often adults and big eagles steal food from younger and smaller birds. Some naturalists believe that the eagles fight over food because robbing a fellow eagle of food is easier than hunting. Others feel they do because they like to fight.

Steller’s Sea Eagle Behavior and Communication

Steller's sea eagles are are motile (move around as opposed to being stationary), migratory (make seasonal movements between regions, such as between breeding and wintering grounds) and solitary. The size of Steller's sea eagles’ home range are not known, but productive nests have been reported to be as close as within 100 meters. [Source: Danielle Nelson, Animal Diversity Web (ADW), Wikipedia]

Steller's sea eagles are solitary birds, congregating with others only to breed or to feed when food is plentiful. Large numbers have been observed congregating at particularly rich salmon rivers and lakes. Steller's sea eagles are commonly seen perching on cliffs above the sea or in large trees. They are active during the day and migrate to warmer areas in the winter.

Steller's sea eagles sense using vision, touch, sound and chemicals usually detected with smell. They communicate mainly through various vocalizations. A deep, barking “ra-ra-ra-raurau” cry is commonly heard. In aggressive encounters, the call is similar to the white-tailed eagles, but deeper. When displays are performed at the beginning of the breeding season, very loud, deep-voiced gull-like call is used.

Steller’s Sea Eagle Mating, Reproduction and Offspring

Steller's sea eagles are monogamous (having one mate at a time) and are often seen in breeding pairs throughout the breeding season. They engage in seasonal breeding usually from February through August. The number of eggs laid each season ranges from one to three. The time to hatching ranges from 38 to 45 days. The average fledging age is 70 days, with independence occurring on average at 70 days. Females and males reach sexual or reproductive maturity at six to seven years of age. [Source: Danielle Nelson, Animal Diversity Web (ADW) /=]

Steller's sea eagle's nest only in eastern Russia, in remote places like the island of Bolshoy Shantar. Klaus Nigge wrote in National Geographic: "Each spring eagles return to the same nest with the same partner. Favorite branches on lookout trees — ones with the best views of their nest and fishing spots — are rubbed bare by sentry duty. Branches, dried grass, and moss form the a ten-foot-wide platform, more than big enough for a kingsize bed. Days are silent but for the chicks; begging cries and its parents warning calls to eagles that fly to coast. Before the salmon run begins, the adults wade into tidepools for small fish to carry to the nest. I saw only the mother feed the eaglet. She tears food into pieces and gently holds them in front of her chick. [Source: Klaus Nigge, National Geographic, March 1999]

Both males and females secure their own breeding territories early in the season and nest building occurs in February or March. Displaying begins in March and consists of soaring high above the breeding area while calling. Typically, a pair maintains two to four nests in one breeding territory and use alternate nests from year to year. Nests are most often built on rocky cliffs or in large trees out of thick branches and can reach a size of two meters across and two to four meters thick.

The egg-laying period normally lasts from April through May. Both parents contribute to raising offspring to independence. Young are altricial, meaning that they are born relatively underdeveloped and are unable to feed or care for themselves or move independently for a period of time after birth. During the pre-birth, pre-weaning, pre-independence stages for young provisioning and protecting are done by males and females. Eggs hatch between May and June, with fledging taking around 70 to 90 days. Steller's sea eaglets are black and fledge in 90 days. Their striking white shoulders, tail, legs and forehead do not develop for six to eight years. Young leave nests by August or September.

Steller’s Sea Eagles, Humans and Conservation

On the International Union for Conservation of Nature (IUCN) Red List Steller’s sea eagles are listed as Vulnerable. The are protected by U.S. Migratory Bird Act. In CITES (Convention on International Trade in Endangered Species of Wild) they are in Appendix II, which lists species not necessarily threatened with extinction now but that may become so unless trade is closely controlled. steady decline. Threats include habitat degradation, deforestation, logging, overfishing and pollution.

Steller’s sea eagles have problems with lead poisoning in their wintering ground in Hokkaido. Populations of one of their main prey — walleye pollack — has been reduced by overfishing. Many eagles have turned to eating sitka deer carcasses left by hunters that are filled with lead shot. Environmentalists suggest requiring hunters to use copper bullets or shotgun shells rather than lead shot.

The current population is estimated at 7,000 and may be increasing. In Kamchatka, 320 pairs have been recorded. An additional 89 nesting areas are not monitored. In the mountains of Koryakan and along the Bay of Penshina, over 1,200 pairs breed and at least 1,400 juveniles occur. About 500 pairs live in the Khabarovsk region of the Okhostsk coast, and 100 on the Shantar Islands. Another 600 pairs occur in the lower Amur. About 280 pairs are on Sakhalin Island and a few are on the Kurile Islands. The total population is around 3,200 breeding pairs. Possibly, up to 3,500 birds winter on Kamchatka, and another roughly 2,000 may occur on Hokkaido. Generally, the species' outlook is favorable. Outside the breeding range, food bases in the principal wintering areas are so far secure. [Source: Wikipedia]

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, Daily Yomiuri, Yomiuri Shimbun, Japan National Tourist Organization (JNTO), New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, BBC, CNN, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated March 2025