The San Diego Zoo received its first Steller’s sea-eagle in 1953 as a gift from a Japanese ornithologist. This bird awed Zoo guests for many years. Our next Steller’s arrived in 1996.
Today, the Zoo is the only place in North America where you can view these impressive eagles. A pair of Steller’s sea-eagles lives in an aviary along the Zoo’s Eagle Trail.
Eagles and humans
Steller’s sea-eagles are a vulnerable species and have been given complete legal protection in Russia, the only place it breeds, and in Japan, where it overwinters. Despite these protections, human behavior continues to harm the remaining sea-eagle population. In Russia, Steller’s are losing their habitat because of the development of hydroelectric power projects and logging in the forested areas where they nest. The rivers where the sea-eagles fish are being contaminated by chemicals from local industries.
In Japan, sea-eagles eat both fish and carrion. Overfishing by humans in Japanese waters has led the birds to scavenge on sika deer remains left by hunters. Eating carrion filled with lead shot from hunters has had devastating effects on the sea-eagle population, leading to the outlawing of lead ammunition on Japan’s Hokkaido Island. As of 2009, the world’s population was estimated at 5,000 birds, but it is slowly decreasing.
Still much to learn
Very little is known about these eagles, especially their early years. Research efforts began in 1992, at Russia’s Magadan State Nature Reserve. In 2006, San Diego Zoo Global and Natural Research, Ltd. teamed up with scientists there to study the movements of young Steller’s sea-eagles in their native habitat to determine the hazards young birds face, in hopes of protecting the species in the wild. Researchers survey nests, and a team member climbs the tree to collect a bird, gently placing it in a bag to be lowered to the ground. The ground crew measures, weighs, and takes tissue samples from the bird. Young eagles get a satellite leg tag so researchers can track its movement.
The team was surprised to discover the extent of persecution these birds are exposed to, despite the species’ protected status throughout its range. Preliminary results show high juvenile mortality, with deaths associated with oil rigs. Nest productivity/chick survival is correlated to snow depth and resulting floods. Fishing and caviar harvesting are major industries in Russia’s Siberia, and they provide offal for sea-eagles to scavenge. However, overfishing can impact the birds’ habits, forcing wintering birds to look inland for food. There, they often prey on deer carcasses, which can contain lead fragments from bullets. Japan responded to this hazard by banning lead bullet use throughout the sea-eagles’ range within their country.
Although legally protected in Russia, Japan, China, and South Korea, other threats to Steller’s sea-eagles include fossil fuel energy developments, wind farms, pollution, habitat loss, hunting, and possibly global warming. By learning more about the threats young sea-eagles face each autumn as they head off on their frosty migrations, it is hoped that this vulnerable bird population may stabilize.
The San Diego Zoo has a pair of Steller’s sea-eagles and has loaned pairs of birds to four other zoos in the US. We hope that seeing these amazing raptors up close will encourage visitors to participate in the conservation of this rare species.
You can help, too!
You can help us bring Steller’s sea-eagles back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy. Together we can save and protect wildlife around the globe.