北海道十勝地方の鳥類

The urban avifauna in the breeding season was studied in Obihiro City containing 150, 000 population from late May through mid-July of 1977 and 1980. Censuses were carried out by a strip census method using the road in four different habitats, namely the wood dominated by Quercus dentata, new and old residental areas with rich vegetation, and residental area with poor vegetation. During the study period each plot was censused 18 times, the total distance of transect censused being 23.4 to 27km in four plots. These distance of transects were sufficient to list up the common bird species occurred in each plot, since the total number of species observed stopped to increase at 11 to 24km of total distance.<br>The number of bird species observed decreased as the proportion of area with vegetation cover decreased, 39 in the wood (plot A), 33 in the new residental area (plot B), 23 in the old residental area (plot C) and 9 in the central part of the city with poor vegetation (plot D). In the plot A dominant bird species were Emberiza spodocephala, Sitta europaea, Dendrocopos major, Passer rutilans, Parus palustris, Parus major and so on. Many of the species recorded there were known to prefer wooded habitats and they comprised 90% of the total number of individuals. Passer montanus was the most abundant in three residental areas. Other dominant species in urban habitats included Emberiza spodocephala, Sturnus cineraceus, Carduelis sinica and Anthus hodgsoni in the plot B, C. sinica, Motacilla alba and Corvus corone in the plot C, and Columba livia var. domestica and M. alba in the plot D. In the plot B, however, a few forest and grassland birds were fairly common because of presence of woodlot and open area covered with grasses. The species which were fairly abundant in the urban habitats were Passer montanus, Columba livia var. domestica, Carduelis sinica and Motacilla alba, and they comprised 53 to 99% of total number of individuals there. Of them first two species were the birds typically associated with the urban environment.<br>The species diversity (H') reduced as the vegetation cover reduced, being the highest in the wood and the lowest in the residental area with poor vegetation. The index of similarity was high between the avifauna in plot C and that in plot D, and low between the avifauna in plot C and that in other urban habitats.