The Birds of Bibai, Central Hokkaido

Abstract

Observations were made on birds at Bibai, situated in the northern part of Ishikari Plain, central Hokkaido, from April 1966 to November 1973. Bibai occupies an area of 275 km2. The western half is occupied largely by cultivated fields, greater part of which is rice paddies and the eastern half is hills covered with deciduous trees. There are residental portions along the artery street runing from north to south. Mean temperature showed 6.8°C, varying from -8.0°C in January to 21.9°C in August. There was snow cover which attained a depth of 1 m from late December to early March.A total of 105 species of birds were recorded during the study. In the present study, the birds fell into resident, summer visitor, winter visitor or transient according to seasons that they occur in Hokkaido. Summer visitors and residents included 57 and 30 species, respectively. The remaining was winter visitors, transient, or rare species. They were recorded from Ishikari Plain by previous workers except for Cygnus olor which is considered to be a fugitive from a park. By the present study it was appear that Motacilla alba, Turdus naumanni and Sturnus cineraceus wintered in small numbers in Bibai. In addition, a indirect evidence showing the breeding of Zesterops palpebrosa was obtained.The number of species increased with summer visitors arriving at from April to June and decreased from October to March of next year. Therefore the winter avifauna was characterized by rather small number of species as compared with that of central Honshu.The study area includes deciduous forests, cultivated fields, bogs, swamps, riserviors and residental portions as habitats of birds. Consequently the avifauna of Bibai consists of forest and grassland birds, waterfowl and birds occurring at residental portions. Of forest birds, however, species preferring coniferous forest occured only in winter. Locustella ochotensis, which occures ordinaly in grassland of northern and eastern Hokkaido, was not recorded from Bibai.