First, who the eagle is and how big it grows; 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, and 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. One idea is that Steller's sea eagles are glacial relics that evolved on the narrow northeast Asian coast and stayed there through several Ice Age cycles.

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

Now, where the eagles go in winter. In the 1997-98 satellite study, 19 young eagles were followed south and 16 of them reached wintering areas. Tracked young eagles spent winter in one to three subareas. Tracked eagles from Magadan crossed an average of 11.6 degrees of latitude on migration, compared with 2.1 for eagles from Kamchatka and 1.1 for Sakhalin. 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. Hundreds of Steller's sea eagles 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. Many fly south to Japan in winter, but some stay in Kamchatka and move to open water.

Hokkaido, in Japan, is where two linked stories meet: deer and lead. 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; a satellite-tracking study found that 35% of eagles overwintering in Hokkaido used mountain areas for at least some time, where they scavenge deer. Lead poisoning of Steller's sea eagles in Japan was first confirmed in 1996, and by 2007, 129 Steller's and white-tailed eagles had been diagnosed as lead poisoning fatalities in Japan. Hokkaido began banning lead rifle bullets for hunting sika deer in 2000 and lead shot pellets in 2001, 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. As of November 2026, a 2015-2018 study of birds found dead in Japan found that 9 of 34 (26.5%) had liver lead above the level for lead poisoning, and an earlier study found that 42% of Steller's sea eagles (18 of 43) tested from 2004 to 2015 in Hokkaido had lead above the poisoning level.

Here is how researchers have studied the eagles. 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. Scientists know little about Steller's sea eagles because their homes in the Russian Far East are remote, and that is why researchers use satellite tracking. To tag young eagles, scientists survey nests, and a team member climbs to a nestling and lowers it in a bag. A ground crew measures it, weighs it, takes tissue samples and fits a satellite leg tag. Scientists on Sakhalin and the Lower Amur collected most nest data from early July to late August, when nestlings are near fledging age and nest results are easiest to judge.

Last of the numbers, how many eagles there are. 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. No one knows for sure how long they live in the wild. As of November 2026, estimates of the world population differ: 3,600 to 3,800 birds (BirdLife International, 2016) or 6,000 to 7,000 (Masterov and others, 2018). As of November 2026, another estimate puts them at around 5,000 birds. In 2000, scientists estimated between 3,200 and 4,200 breeding pairs. As of November 2026, 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.

Finally, how the eagles raise their young. Studies in 2004-2017 on Sakhalin and in the Amur region found about 0.53 and 0.61 fledglings per occupied territory a year, compared with about one in earlier decades; a 2004-2019 study found one nesting territory produced 0.51 fledglings a year on the Lower Amur and 0.35 a year on Sakhalin Island. Researchers count nesting territories rather than single nests: nests closer than 400 meters to each other were counted as one territory. A full clutch holds one or two eggs, rarely three, and a third nestling usually does not survive even if it hatches; a pair often returns to the same nest each year and adds more branches to it. The eggs take about 38 to 45 days to hatch; a chick 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

• fledglings: young flyers
• territory: nest area
• estimates: careful guesses
• relics: old survivors
• latitude: north-south position