Changes in a breeding bird community over 27 years in a mixed forest in a suburb of Morioka City, northern Honshu, Japan

Abstract

A breeding bird community in a mixed forest (28ha) in a suburb of Morioka City, Iwate Prefecture, northern Honshu, Japan, was investigated for 27 years between 1970 and 1996 by the territory mapping method. No significant difference was found in breeding pair density during the period, while a slight decrease was found in the number of breeding species. Composition of the bird community changed significantly during the period. Among the residents, Parus group densities increased mainly with the improvement of nest box instalation techniques. Picidae group densities increased in response to an increase of dead trees. Corvus group densities increased in accordance with an increase of human visitors in the study area. Mid-sized, short-distant migrants (Streptopelia orientalis, Hypsipetes amautotis, etc.) notably decreased due to an invasion of Accipiter gentilis and an increase in nest attacks by crows. Small sized species (Zosterops japonica and Carduelis sinica) increased without known reasons. Among the summer visitors, although most species decreased in accordance with the other areas of Japan, densities of Ficedura narcissina and Cettia squameiceps increased. A decrease in overwintering habitat in South-East Asia due to logging or other developmental actions may be a cause of the general decrease in the summer visitors.