We studied White-tailed Haliaeetus albicilla and Steller's Sea Eagles H. pelagicus in western Hokkaido, along the sea terrace of the Japan Sea, to determine the factors affecting the frequency of flight activity. We analyzed the effect of nine factors (temperature, atmosphere, precipitation, hours of sunshine, wind speed, index of west wind speed, index of north wind speed, survey year and time of day) on the flight frequency of eagles. Index of west wind speed was the most important factors affecting the flight frequency of both White-tailed and Steller's Sea Eagles. Westerly winds interact with the slopes of the sea terrace to create favorable updrafts for flying.
2010 by Japan Bird Research Association