Abstract
The relative abundance of Tree Sparrow Passer montanus were compared between 1991-2004 and 2006 in 17 residential areas of Hokkaido. Average numbers (±SD) of birds counted in a transect 2 km long and 50 m wide decreased significantly from 24.6±7.5 in 1991-2004 to 14.5±8.1 in 2006. Relative abundance increased in two study areas, remained unchanged in one area and decreased in 14 areas. Change rates (CR, Number of birds counted in 2006/number of birds counted in 1991-2004) exceeded 1.0 in two areas located in mountainous localities, but were 0.71-1.00 in south-western and eastern parts and less than 0.71 in central parts.
