The distribution of breeding birds in Hokkaido, Japan

Abstract

In Hokkaido most bird species (e.g., Black-faced Bunting Emberiza spodocephala, Carrion Crow Corvus corone, Large-billed Crow C. macrorhynchos, and Japanese Tit Parus minor) are distributed throughout all districts of the prefecture during the breeding season. Some species are more commonly distributed in southern (Lesser Cuckoo Cuculus poliocephalus and Barn Swallow Hirundo rustica), south-western (e.g., Honey Buzzard Pernis ptilorhynchus, Japanese Thrush Turdus cardis, and Japanese White-eye Zesterops japonicus), eastern (Lesser Spotted Woodpecker Dendrocopos minor), north-eastern (Common Merganser Mergus merganser) or northern areas (Yellow Wagtail Motacilla flava). A few species (e.g., Black-browed Reed Warbler Acrocephalus bistrigiceps) have a different distribution pattern and found in coastal areas and along the middle and lower reaches of rivers. Grassland birds (e.g., Eurasian Skylark Alauda arvensis and Chestnut-eared Bunting Emberiza fucata) occur mainly on plains and in basins with grasslands. In contrast, forest birds (e.g., Hazel Grouse Tetastes bonasia and Japanese Robin Luscinia akahige) except those species occurring also in agricultural lands, are distributed mainly in mountainous forest-covered areas. The range of birds occurring at high elevation (Red-flanked Bluetail Tarsiger cyanurus) are narrower than those of birds occurring from low to high elevation. The abundance of species occurring in south-western areas (Japanese Thrush) increases in line with rising air temperature. Conversely, the abundance of species (Common Merganser) increases as the air temperatures decline. The abundance of birds occurring in high elevation (Red-flanked Bluetail) increases as the altitude increases. These facts suggest that air temperature is one important factor determining the distribution of some species. The number of species with a south-western type distribution is greater than that of species with a north-eastern type. This is considered to be because of the greater similarity between the avifaunas of Hokkaido and Honshu than between those of Hokkaido and Sakhalin or Primorye.