Trends of population, distribution and habitat conditions of Northern Goshawk estimated from 20 years of rescue records from western Kanagawa Prefecture

Abstract

We analyzed data of over 20 years from the Kanagawa Prefecture Nature Environment Conservation Center in the the western part of Kanagawa Prefecture to study the long term, regional scale changes in the population, distribution and habitat conditions of the Northern Goshawk Accipiter gentillis fujiyamae. From 1990 to 2000 the number of rescued Northern Goshawks gradually increased and then stabilized or decreased slightly. In the 1990s, rescue locations of Northern Goshawk were in the western areas of the Sagami River, thereafter expanded to the eastern areas of the river, and then from 2008~2012 the rescue locations were in the western area of the river again. From 1993~2012 (20 years), the main habitat of the area where the birds were rescued was broadleaf deciduous and /or coniferous woods which eventually changed to urban areas. These results suggest that the population of Northern Goshawk in the western areas of Kanagawa Prefecture increased in number with expansion of range to eastern, more urbanized areas until 2000, but then it has stabilized or decreased slightly.