北海道におけるカワアイサの繁殖期の分布

抄録

A distribution map of the Common Merganser Mergus merganser in Hokkaido, Japan, is presented based upon data obtained by transect and spot censuses, records from the literature, and unpublished personal records. The Common Merganser occurred on rivers, lakes and reservoirs which were situated mainly to the east of Hidaka Mountains and Daisetsu mountainous area and north of 43°20′N. Air temperatures during breeding season in these areas are lower than in other areas. It is considered that air temperature during breeding season is one of the factors determining the distribution of the species.