Natural elements and anthropogenic disturbance affecting the distribution of water birds on a river in winter

Abstract

The relationships between natural elements, anthropogenic disturbances, and water bird species distribution were studied along a mid-stream section of the Abukuma River, northeastern Japan, in winter. Of the 17 bird species recorded in the study area, 14 were significantly affected by one or more items among the four explanatory variables in the multiple regression analysis. The distributions of Long-billed Plover Charadrius placidus and Little Egret Egretta garzetta were significantly correlated with the riffles. Conversely, Spot-billed Duck Anas poecilorhyncha distribution was significantly correlated with pools. Common Merganser Mergus merganser, Great Cormorant Phalacrocorax carbo and Mallard A. platyrhynchos were significantly correlated with river confluences. The distributions of Whooper Swan Cygnus cygnus, Tundra Swan C. columbianus, Northern Pintail A. acuta, Eurasian Wigeon A. penelope, Common Pochard Aythya ferina and Tufted Duck A. fuligula were significantly correlated with sites where people feeding birds. Grey Heron Ardea cinerea and Great Egret E. alba were significantly correlated with areas into which neither people nor vehicles intruded. Common Teal A. crecca showed no preference for any particular area. This study suggests that anthropogenic disturbances are critical factors affecting the distribution of water birds, and that preserving landscape elements composed of natural geographical features and vegetation are important for conserving biodiversity in river ecosystems from the standpoint of water bird communities in winter.