The Steller's sea eagle is named after Georg Steller, a German biologist who explored Kamchatka and Alaska in the 1700s. Its genus name, Haliaeetus, expresses that the principal diet of sea eagles is fish. It is the largest of the sea eagles and is called the heaviest known eagle, and it ranks with the harpy eagle and the Philippine eagle among the largest birds of prey. Animal Diversity Web gives the average mass as 6 kilograms for males and 9 kilograms for females, and a 2009 paper from a Hokkaido wildlife center gives the mass as 5 to 7.5 kg. Females are larger than males.

The eagle's big bill is described as hatchet-like and is suited to tough salmon skin. It uses both eyes together, called binocular vision, to judge where its food is, and it glides on rising warm air instead of flapping all the time.

It hunts from a perch or while flying and catches prey in its talons. Sometimes it stands in shallow water or on ice and grabs fish that swim by. It eats mostly salmon, and also crabs, shellfish, small animals, gulls and carrion, and it will sometimes steal food from other birds. It can use up an entire day's calories by flying for just 45 minutes, so it nests close to its food to save energy. Researcher Alexander Ladyguin says eagles need about 11 minutes of undisturbed feeding time in winter, and four times that in summer, to meet their daily energy needs.

In winter, many Steller's sea eagles fly south to Japan, but some stay in Kamchatka and move to open water. Hundreds gather at Kuril Lake in Kamchatka each winter to feed on salmon, and the lake mostly stays free of ice because of springs, wind and its closeness to the sea.

In the 1997-98 satellite study, scientists fitted 29 nestlings with transmitters. Nineteen young eagles were followed south and 16 of them reached wintering areas. They spent winter in one to three subareas, and the first wintering subareas averaged 274 square kilometers, the second 529 and the third 1,181. Most eagles from Magadan and the Amur migrated down the western edge of the Okhotsk Sea, while birds raised in Kamchatka moved down the Kuril Islands. Before migrating, they stopped at pre-migration sites on the lower parts of rivers, which may be places where many dead salmon are found after spawning, and spring migration back north started between 2 February and 31 March.

When fish became harder to find in winter, dead deer became a major food for Steller's sea eagles wintering on Hokkaido, according to a 2009 paper. In spring 1995 satellite signals showed a tagged eagle had moved inland and stopped moving, and a colleague found it eating the remains of a deer. A satellite-tracking study found that 35% of eagles overwintering in Hokkaido used mountain areas for at least some time, where they scavenge deer and can be exposed to lead.

Lead poisoning of Steller's sea eagles in Japan was first confirmed in 1996. Hokkaido began banning lead rifle bullets for hunting sika deer in 2000, and lead shot pellets for sika deer in 2001. Hokkaido extended the ban in 2004 to all hunting of large animals, and since 2014 hunters may not even carry lead rifle bullets, slugs or large shot pellets. By 2007, 129 Steller's and white-tailed eagles had been diagnosed as lead poisoning fatalities in Japan.

From 2004 to 2019, researchers monitored 438 nesting territories on Sakhalin Island and 350 on the Lower Amur over 12 field seasons in each area. They count nesting territories rather than single nests: nests closer than 400 meters to each other were counted as one territory. Scientists collected most nest data from early July to late August, when nestlings are near fledging age and nest results are easiest to judge.

A full clutch holds one or two eggs, rarely three, and a third nestling usually does not survive even if it hatches. Home range sizes are not known, but productive nests have been found as close as 100 meters apart. A pair often returns to the same nest each year and adds more branches to it.

Scientists know little about Steller's sea eagles because their homes in the Russian Far East are remote. Kamchatka was a key Soviet military outpost and was off-limits to scientists until the mid-1980s. Conservation research began in 1992 at Russia's Magadan State Nature Reserve, and in 2006 the San Diego Zoo and Natural Research Ltd. joined Russian scientists to study the movements of young eagles. That is why researchers use satellite tracking.

As of November 2026, estimates put the world's Steller's sea eagles at around 5,000 birds. Several sources say the number is declining. As of November 2026, the IUCN Red List lists the eagle as Vulnerable. Logging that harms their forest habitat is named as a threat.

The eagles are protected by law in Russia, Japan, China and South Korea. A 2008 magazine report said about 10 percent of their nesting and wintering grounds are protected in nature preserves in Russia and Japan.

The eggs take about 38 to 45 days to hatch. A pair usually raises just one chick. A chick is covered in soft gray-white down that slowly changes to brown feathers, and it learns to fly when it is about 10 weeks old. Researcher Alexander Ladyguin found that nestlings multiply their weight 40 times in less than two months on a diet of salmon.

Words to know

• genus: a group name
• territories: nest areas
• subareas: smaller areas
• carrion: dead animal
• fledging: leaving the nest