The Steller's sea eagle is the largest of the sea eagles and is called the heaviest known eagle. It ranks with the harpy eagle and the Philippine eagle among the largest birds of prey. Its wings can stretch up to 8 feet from tip to tip. Female Steller's sea eagles are larger than the males, and a female can weigh up to about 20 pounds (9 kilograms).

The eagle's big bill is described as hatchet-like, and it 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.

Steller's sea eagles eat mostly salmon, a kind of fish. Besides fish, they eat crabs, shellfish, small animals, gulls and carrion, which is an animal already dead. A Steller's sea eagle 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.

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

In 1997 and 1998 scientists fitted 29 Steller's sea eagle nestlings with satellite transmitters, and 24 of them gave useful data about what they did after leaving the nest. Each transmitter weighed about 65 grams and was worn like a backpack on a Teflon ribbon, with a sewn link meant to wear away so the pack falls off. Young eagles left the area around the nest between 9 September and 6 December, and most left between 14 September and 21 October.

The young eagles took 5 to 116 days to reach their first winter homes, and their migration averaged 51.3 kilometers a day. A published analysis of tracked young eagles found they averaged 47.8 km a day on migration without stopovers, but only 22.9 km a day when stopovers were counted. Most young 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, young eagles stopped at pre-migration sites on the lower parts of rivers, which may be places where many dead salmon are found after spawning. Spring migration back north started between 2 February and 31 March for the tracked young eagles.

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.

Conservation research on Steller's sea eagles began in 1992 at Russia's Magadan State Nature Reserve. In 2006 the San Diego Zoo and Natural Research Ltd. joined Russian scientists to study the movements of young Steller's sea eagles. Scientists know little about the eagles because their homes in the Russian Far East are remote. They are protected by law in Russia, Japan, China and South Korea.

As of November 2026, estimates put the world's Steller's sea eagles at around 5,000 birds, and several sources say the number is declining. The IUCN Red List lists the eagle as Vulnerable. Logging that harms their forest habitat is named as a threat. Scientists know of no animal that preys on adult Steller's sea eagles.

A pair often returns to the same nest each year and adds more branches to it. A female lays one to three eggs in spring, and the eggs take about 38 to 45 days to hatch. A pair usually raises just one chick, even when more than one egg is laid. 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

• transmitter: signal sender
• stopovers: rest stops
• nestlings: nest babies
• spawning: laying eggs
• binocular: using both eyes