Difference in distribution between the White-tailed eagle and the Steller's sea eagle on their wintering grounds. : On Hokkaido, Japan.

Sammanfattning: The White-tailed eagle (H. albicilla) and the Steller's sea eagle (H. pelagicus) overwinter in the same region of Japan: North-western Hokkaido. To examine how and if these two species compete at their overwintering grounds the following questions were asked: are they evenly distributed over this region and do they compete over space and resources? For the period 2015-2019, I found that the two species were not evenly distributed over the region, and that H. pelagicus is the most common species and does occur over the whole area. At a more detailed study at Lake Abashiri performed in 2019-2020, results showed that H. albicilla was the most common species, and that the distribution of the eagles was determined by the availability of food from anthropogenic activity. The species competed for food resource, fish, and H. pelagicus was the stronger competitor in terms of attacks against heterospecifics. They were less aggressive, but more successful when attacking compared to the White-tailed eagle.