Effects of environmental and management factors on the structure of bird communities in the grasslands of northeastern Tochigi, central Japan

Abstract

Bird communities were surveyed in grasslands and adjacent forest edges in 11 and 14 pastures and meadows of northeastern Tochigi, central Japan, from May to early August and May to June in 2000 and 2001, respectively. Using the strip transect method, 36 bird species were recorded. They were divided into six ecological groups depending on their occurrence in the two types of habitat: six grassland specialists including the Eurasian skylark (Alauda arvensisL.) and the fan-tailed warbler (Cisticola juncidis (Rafinesque)), two semi-grassland species including the barn swallow (Hirundo rusticaL.) and the cattle egret (Bubulcus ibis (L.)), nine semi-forest species, such as the Eurasian tree sparrow (Passer montanus (L.)), the Japanese bush warbler (Cettia diphone (Kittlitz)), and the brown-eared bulbul (Hypsipetes amaurotis (Temminck)), six forest specialists, such as the eastern great tit (Parus minorL.), seven generalists, such as the oriental greenfinch (Chloris sinica (L.)) and the black-eared kite (Milvus migrans (Boddaert)), and six other infrequent species. The bird communities were separated into three groups using principal component analysis (PCA). Combined PCA and multiple regression analyses indicated that the structure of the bird communities was influenced by the height and species richness of vegetation, altitude, and mean annual temperature as major factors.