BIRD SURVYE OF OZE IN SUMMER, 1974-1978

Abstract

Community structures and vertical distributions of woodland birds were investigated in the breeding season from 1974 to 1978 in Oze of Gunma prefecture. Line transect method was used for the estimation of the numbers of species and individuals. Results obtained were as follows.1. From this survey, 93 species were recorded, including Prunella rubida and Prunella collaris in high mountains area.2. Cettia diphone and Parus ater of transient and Phylloscopus borealis of summer visitor, which are insectivorous birds, had priority over others, while Pyrrula pyrrula, Nucifraga caryocatactes and Garrulus glandarius of seed and leave feeder distributed all over the investigative area inspite of small numberes, these being characteristic of the Honshu-subalpine coniferous forest.3. Phylloscopus tenellipe and Emberiza variabilis were recorded concentrically at the ecotone of subalpine coniferous forest and broad-leaved deciduous forest.4. Dominant species of Oze were Cettia diphone (20.0%), Parus ater (15.8%), Phylloscopus borealis (14.3%), Erithacus akahige (5.2%), Tarsiger cyanurus (3.1%). These five species occupied 58.4% of all, and yet, constant bird community was maintained in Oze because of many species of birds lived in this area. 5. The density of Sturnus cineraceus, Phylloscopus occipitalis and Phylloscopus tenellipes were higher in May than that in August, and in August these species already transferred or dispersed somewhere.6. Six species of Cettia diphone, Phylloscopus borealis, Parus ater, Corvus macrorhynchos, Troglodytes troglodytes, and Erithacus akahige were widely distributed from low mountain zone to high mountain zone, and these six species were considered to be the fundamental constitution of bird community in the breeding season of Oze.7. As a limiting factor of vertical distribution of each species, a vegitational construction of the habitat and altitude were considered to be the main factor. For example, Phylloscopus borealis were distributed in Abies Mariesii forest, P. tenellipes in the ecotone between Fagus crenata forest and Abies Mariesii forest, P. occipitalis in Fagus crenata forest.8. Sturnus cineraceus was most dominant species in Ozegahara. Sturnus cineraceus, Corvus macrorhynchos and Alauda arvensis were considered to have close correlations with people.9. All over Oze, the population of Delicon urbica were about 10, 000 in 1970 but in 1978 it was about 4, 000.