We investigated the caching behaviour of Japanese Lesser Sparrowhawks Accipiter gularis during the breeding season in Tokyo and Utsunomiya, central Japan. Observations were made from April to July 1987-1993 in Tokyo and 1991-1993 in Utsunomiya. A total of 46 caching behaviours were observed. All of the prey items cached were small and medium-sized birds, especially Tree Sparrows Passer montanus (65.2%, 30 of 46). Hawks cached prey that were half eaten by females, and prey which was not taken by the female in attempted prey exchanges initiated by the male. Many caches were carried out in the incubation and early nestling periods. Hawks stored prey on gnarled, broken twigs and leaf clumps on horizontal branches 7-8m in height and within a few meter to 50m apart from the food exchange site. Some birds used a few definite sites, and others used many places within a range of 50 × 30 m as caching sites. When hawks flew to caching sites with prey, they placed the prey carefully, and push it several times with their legs and beak. At least 11 stored items were retrieved within 3-247 min. (mean ±S.D., 78.5 min. ±73.2) after caching. Although 8 stored items were stolen by Azure-winged magpies Cyanopica cyana, most cached prey may be retrieved.
Breeding bird communities were investigated monthly from May to July 1991, and in June 1992 and 1993, at the foot of Mt. Toyama in Oku-Nikko, northern Kanto. Two areas were studied. Both contained deciduous broad-leaved forest, one with a mixture of coniferous trees (A) and the other with a larch plantation (B). Thirty-one species were observed, 24 in area A and 21 in area B, with 14 species common to both areas. Total numbers of individuals were always greater in area A than in area B during the study period. The two most abundant species were Parus ater (14.7-17.8% in area A, 8.3-25.0% in area B) and Cettia diphone (12.6-16.7% in area A, 20.1-33.6% in area B). High density of four species of Cuculidae (9.9-12.3%) appeared in area A. Cuculus poliocephalus did not appeared in area B, though its host species, C. diphone was in high density, and Cuculus canorus appeared in both areas, though its host species, such as Lanius bucephalus and Emberiza cioides was in low density.
A monthly line transect and capture survey of the forest bird community in a forest in the Massif Tsukuba for five years from autumn 1988 showed that the introduced Red-billed Leiothrix had increased in number. In the first three years only one individual was captured in October 1989. However, in 1992 and 1933 this species was recorded frequently as a common species in both survey methods. The increase in the number recorded in the study site could suggest the increase in the whole population size in the Massif Tsukuba.