Birds of Tokachi District, Hokkaido

5. Birds along the lower reaches of the Tokachi River

Abstract

Bird populations were censused using the line-transect method in four areas of shrub-grassland along the lower reaches of the Tokachi River in eastern Hokkaido, from mid-May to early July, 1981-87. One transect of 50m width and 2 to 3.3km length was established in each area. A total of 47 bird species were recorded along the four transects. Shannon-Weaver's species diversity indices (H') was calculated based on numbers of birds counted in May and June. The resuslts were: 3.49 in the transect A, 3.13 in the transect B, 3.94 in the transect C and 3.55 in the transect D. The most common species, that is, those with a relative dominance percentage of more than 2 percent, were the shrub-grassland birds: Gallinago hardwickii, Alauda arvensis, Erithacus calliope, Saxicola torquata, Locustella ochotensis, L. lanceolata, Acrocephalus bistrigiceps, Emberiza fucata, E, aureola, E. spodocephala, E. schoeniclus and Uragus sibiricus. These species prefer open habitats. Other less common species were: Streptopelia orientalis, Motacilla alba, Turdus chrysolaus, Locustella fasciolata, Carduelis sinica and Sturnus cineraceus. The occurrence of these species depended upon the presence of woods or open areas without vegetation. More shrub-grassland birds occurred in open habitats along the river than in agricultural lands in the same district. Although riverine and adjacent areas have been modified by various riparian works, they continue to provide an important habitat in the reduction of native grassland habitat in low altitude areas.