An Approach to the "Eco-city" Coexistent with Birds

Abstract

Because Japanese cities have been developed for the purposes of pursuing only economy and industry, they are usually short of natural habitats, consisting mostly of nonorganic environments with few wildlife. Recently, however, it is strongly expected that new-styled cities with a variety of wildlife will be developed. In doing so, it is essential to know the ecology of wildlife, especially their habitat needs, and to apply that information to the city plan. In this paper, I review and discuss information concerning the relationships between terrestrial bird communities and the environmental factors of urban areas and, by using them, propose some methods for introducing and/or reintroducing those environmental factors needed to develop an "eco-city". The principal assertions are as follows:
1) Urban bird communities usually depend on vegetational factors such as amount, structure, species composition and dispersion of vegetation. Increase of vegetation volume may be most important for introducing a high diversity bird community into an urban area. An increase of green volume in an urban area could be promoted by adopting vegetation management by avoiding over-pruning, and a city plan that provides for increasing green space by aggregating houses (apartments, town houses, terrace houses), road systems with culs-de-sac, provision of underground car parks and the introduction of vegetation to walls and roofs.
2) The bird communities of "green islands" isolated in urban areas are usually affected by factors such as the shape, size and distance from adjacent green areas. Further, these relations may vary depending on localities, seasons and methodologies for analyses. Therefore, we need specific local surveys. For the present, Diamond's proposition (1975) will be effective as a guide, and the garden city with an extensive green area proposed by Howard (1902), could be considered as an ideal style of city favorable for inhabitation by a variety of birds.
3) Urbanized birds have the ability to use buildings as nestsites, and to use supports by man such as artificial feeding and nest boxes. However, since dependence on these man-made resources may benefit only a limited number of avian species, and possibly deprive natural resources from them, such supports should be avoided. From the same viewpoints, the introduction of exotic species should be prohibited since they may harm the bird communities and associated ecosystems natural to the areas.