Changes of Distribution of the Eurasian Magpie Pica pica in the Iburi Region of Southern Hokkaido

Abstract

The Eurasian Magpie Pica pica was first recorded in Muroran City, Iburi District, southern Hokkaido, in 1984. We examined distribution changes of this species in each decade of 1984–2013 based on observations recorded by local birdwatchers. During the first decade (1984～1993) Eurasian Magpies stayed and bred in the original area, before expanding their range from the city eastward along the seaboard and further eastward beyond the study site in the second decade (1994～2003). In the third decade (2004～2013), however, they started to expand westward. It is assumed that the hills extending to the coast to the west of the city had prevented them from westward expansion. Although their breeding rate is not high, the observation of a flock of 10 birds in the third decade suggests that the population density has increased to a level that has triggered the expansion in a new direction.