Preference of birds for undergrowth in a Tokyo suburban deciduous forest

抄録

In a suburb of Tokyo in the winter of 1991/1992 and in the summer of 1992, uses of vegetation by birds were surveyed at seven sites within broad-leaved deciduous coppices and the effects of undergrowth removal on birds were examined. More than 80% of bird species were observed in the upper layer (>2 m high) of every site. With a few exceptions, the number of bird species was smaller in the lower layer (<2 m high) than in the upper layer, and smallest at sites without undergrowth. Well-grown undergrowth was attractive to several bird species such as blackfaced buntings (Emberiza spodocephala) and red-flanked bluetails (Tarsiger cyanurus) in winter, and Siberian meadow buntings (E. cioides) in summer. The preferennce of some bird species for specific layers was dependent on the amount of vegetation. The exposed ground in forests without undergrowth was frequently used by a few species of birds such as feral pigeons (Columba livia), tree sparrows (Passer montanus) and grey starlings (Sturnus cineraceus), all of which adapted to unforested urban habitat. Thus, it could be concluded that undergrowth removal negatively affects bird species diversity in suburban coppices.