2013 Volume 9 Pages A13-A22
The population of Eurasian Tree Sparrow Passer montanus has declined in Japan. The cause of the decline is considered to be a lack of suitable nest sites on residential and commercial buildings built more recently. When compared to older building styles, new construction lacks external cavities that can be utilized by sparrows as nesting sites, and therefore the reproductive rates have decreased due to a lack of nesting sites as newer construction replaces older structures. This study examines that effect by comparing the density of Eurasian Tree Sparrow nests observed in new residential areas to that of old residential areas. Paired study sites of residential areas with new and old construction were located in Iwate and Saitama Prefectures, Japan. In Iwate, the density of sparrow nests in the residential area built around 1980 was 3.8 times as high as that in the area built around 2000. Likewise, in Saitama, the nest density in the residential area built around 1960 was 4.8 times as high as that in the area built around 2000. These results demonstrate that the change in residential construction styles, which typically has well-sealed houses with few external cavities, plays an important role in the decline of the Eurasian Tree Sparrow population in Japan.
