抄録
A monthly line transect and capture survey of the forest bird community in a forest in the Massif Tsukuba for five years from autumn 1988 showed that the introduced Red-billed Leiothrix had increased in number. In the first three years only one individual was captured in October 1989. However, in 1992 and 1933 this species was recorded frequently as a common species in both survey methods. The increase in the number recorded in the study site could suggest the increase in the whole population size in the Massif Tsukuba.
