京都市街地都市林におけるアオバズクの生息環境適合度モデル

Abstract

Brown Hawk Owl (Ninox scutulata) is a migratory insectivorous bird which breeds in tree cavities, and a target species for old woods in urban areas of Japan. Population of the owl is decreasing recently because of diminishing of old woods in Japan and also in tropical rain forests: their habitats during non-breeding season. A habitat model using statistical methods is a good tool to answer the question how much forest is required for conservation of a target species. We made a habitat model for the owl using a logistic regression model. We searched for owls by examining almost every large tree with cavities in a 25 urban area in Kyoto City during the breeding season (May to July) of 2002. Fourteen trees determined to be habitats of owls and 15 trees with cavities but without nests were found. Applying logistic regression analysis with the stepwise method and AIC, the area of tree cover and the area of urbanized area within a radius of 100 m were determined to be variables for the habitat model of the owl. From the result, at least 1.1 ha of woods including an old tree with a cavity is necessary for conservation of the owl habitat.