Effect of Aquatic Insect Emergence on the Bird Community in Riparian Forest

The role of stream insect in sustaining a riparian bird community was studied in Kakita Stream, central Japan. Kakita Stream is a spring-fed stream with constant water discharge and temperature throughout the year. Seasonal dynamics of aquatic insect emergence and the dynamics of bird abundance in riparian forest were monitored at Kakita Stream and compared with a control site, Kano River, which is an ordinal stream showing greater fluctuations in water temperature and discharge. Higher abundances of aquatic insect emergence were observed at Kakita Stream compared with Kano River, especially in winter. Kakita Stream acted as a wintering place for many forest birds, as evidenced by the higher abundance of birds compared with the Kano River site. In summer, however, there was no difference in abundance between the Kakita and Kano sites, indicating that the riparian forest of Kakita Stream did not act as a better breeding place than Kano River. This may be because the area of riparian forest around Kakita Stream is insufficient for forest birds to breed. This finding might suggest ways in which the Kakita Stream, including the riparian forest, can be managed optimally in the future.