Seasonal change in habitat use in Steller's sea eagles

Abstract

Habitat-use by Steller's sea eagle Haliaeetus pelagicus, categorized as Vulnerable on the 2002 IUCN Red List, was studied using satellite-tracking. This migratory species breeds in eastern Russia and mostly overwinters in Hokkaido, Japan, and the southern Kuzil islands. Locations of eagles were classified as being river, sea, lake, or other habitat. In autumn, eagles mainly used river habitats, probably because of the availability of abundant post-spawn dead salmon. In winter about one third of eagles continued to be located on rivers, with others on sea coasts and lake sides. During the spring migration and breeding season habitat use by adult eagles probably reflected the variety of habitats in which breeding occurs. At that time, sub-adult eagles were located mainly on the sea coast, probably in places where food supply was sufficient and there were few territorial eagles. In Hokkaido 35% of overwintering eagles used mountain areas for at least some time. It is known that eagles using mountain areas in Japan in winter scavenge upon the carcasses of sika deer Cervus nippon killed by hunters, and are thus exposed to possible lead poisoning. The satellite tracking highlights the importance of several habitats within the range of this species, changes in which could affect its conservation status.