Population decline of Japanese Lesser Sparrowhawks breeding in Tokyo and Utsunomiya, central Japan

Abstract

The breeding distribution, breeding success and nest site selection of Japanese Lesser Sparrowhawks Accipiter gularis were studied in the suburbs of Tokyo and Utsunomiya, central Japan from 1987 to 2005. The number of nest sites increased from the late 1980s to the early 1990s but decreased thereafter in both of the study areas. After the late 1990s the hawks increasingly abandoned their nests because Jungle Crows Corvus macrorhynchos attacked them. In Tokyo, few sparrowhawks bred in a large grove dominated by Jungle Crows after the mid 1990s and bred mainly in a small grove with few pine trees where they selected tree species other than pines for nesting in. In Utsunomiya, a large number of Japanese Red Pine trees remained in a small grove and there hawks used pine trees for nesting in more frequently than in Tokyo. These results suggest that the increasing population of Jungle Crows has detrimental effects on the breeding distribution, the breeding success and nest site selection of Japanese Lesser Sparrowhawks.