Relationships between waterbird communities and environmental factors in urban lakes in suburb of Tokyo

Abstract

The relationships between waterbird communities and environmental factors were examined in 28 urban lakes, located in Tokyo suburbs, during 1991-92. Twenty factors concerning lake morphology, water quality, isolation from other wetlands, land use of neighboring area, and human disturbance were included in multiple regression analyses. The lake size was a significant positive factor regarding the number of bird species during both the wintering and breeding seasons. Lakes surrounded by an artificial fence or littoral emergent vegetation tended to support more species than open lakes in the wintering season. Furthermore, circularity and shallowness of the lakes were also a significant positive factor regarding the number of bird species in winter. Human disturbance through activities such as fishing and boating was a negative factor regarding winter bird density. During breeding season, the amount of emergent vegetation and the presence of islands in the lakes were positive factors, while the distance to the nearest river was a negative factor in regard to bird density. Dominant bird species were influenced by the amount of emergent vegetation, land use of neighboring areas and human disturbance. An increase of emergent vegetation related to the dominance of the Moorhen (Gallinula chloropus). An increase in neighboring residential area and human recreational activities related to changes in dominant duck species -from ducks which use the lake for resting, to ducks which use the lake for feeding. From this relationship it could be suggested that, in order to improve urban lakes as effective waterbird habitat, lakes should be large, surrounded by a fence or emergent vegetation, contain islands, located close to other wetlands and kept undisturbed from human recreation activities.