The status and breeding biology of Ospreys in Hokkaido, Japan

Abstract

The status and distribution of the Osprey (Pandion haliaetus) in Japan is poorly known, although it is considered as a near threatened species nationally. We studied the status, distribution and habitat characteristics of Ospreys breeding in Hokkaido, the northern island of Japan, from 2002 to 2003. During this period we located 62 Osprey nests and confirmed breeding in 8 of 14 districts of Hokkaido, indicating a sizable population breeding in Japan. Most Ospreys occurred in the western part of Hokkaido. We also found nests in two northern (16%) and one central (16%) districts, where breeding had not previously been confirmed, possibly representing a range expansion or previous underreporting. More than half of all nest sites (n = 35) were on rocks or cliffs, while elsewhere in the world nests in such situations appear to be scarce. The distribution of nesting Ospreys is concentrated where the frequency of the White-tailed Eagle (Haliaeetus albicilla) is lower, suggesting that the Osprey's range in these areas is restricted by avoidance of competition with or predation by eagles. The breeding population should be carefully monitored, because human activity at breeding sites or associated foraging sites could affect the population trend. © The Cooper Ornithological Society 2011.