ORNITHOLOGICAL Science

Volume 1 Number 2 September 2002

Hino T
Breeding bird community and mixed-species flocking in a deciduous broad-leaved forest
in western Madagascar.

The breeding bird population of a deciduous broadleaved forest in western Madagascar was censused by means of territory mapping. Despite the foliage structure being simpler, neither species richness nor density was less than those in mature temperate forests. Species diversity was higher in the western Madagascan forest owing to the higher species evenness. Tree-cavity nesters and bark foragers were few because woodpeckers, nuthatches, and tits have not colonized Madagascar. The scarcity of birds nesting on or near the forest floor may be attributable to abundance of nest-predators such as large lizards and snakes in these areas. The bird community was dominated in abundance by the members of mixed-species flocks, almost all of which forage in the canopy. Mixed-flocking can be beneficial for these birds to avoid predation by raptors, which were frequently observed in the canopy. Since most of the flock members had relatively similar territory sizes resulting in similar densities, the high species evenness in this community may have resulted from mixed-flocking by canopy-foraging species.


Kotaka N & Matsuoka S
Secondary users of Great Spotted Woodpecker (Dendrocops major) nest cavities in urban and suburban forests in Sapporo City, northern Japan.

Old nest cavities excavated by Great Spotted Woodpeckers (GSW) Dendrocopos major were examined in two study areas (urban and suburban forests) in Sapporo, the capital city of Hokkaido, northern Japan. Five avian and one mammalian secondary cavity user (SCU) species occupied 47 of 101 GSW cavities inspected. The species composition differed between urban and suburban forests. Avian SCU species occupied GSW cavities more frequently in the urban than in the suburban forests. Tree Sparrows Passer montanus and Chestnut-cheeked Starlings Sturnus philippensis were the only dominant cavity breeding species in the severely fragmented urban forests. Flying Squirrels Pteromys volans were the most dominant users of GSW cavities in the suburban forests. The density of GSW cavities depends not only on natural processes but also on human activities. The suitability of the GSW cavities for certain SCU species decreases with time. To maintain the diversity of cavity-nesting wildlife in urban and suburban areas of Sapporo, preservation of existing trees with GSW cavities as well as providing suitable habitat conditions to support continued production of new cavities is essential.

Amano HE & Eguchi K
Foraging niches of introduced Red-billed Leiothrix and native species in Japan.

Kyushu, southwestern Japan, the introduced population of the Red-billed Leiothrix Leiothrix lutea has increased rapidly and its range expanded considerably since early 1980s. In order to clarify the influences of Red-billed Leiothrix on native bird species, we examined the similarities and differences in foraging patterns among species occurring in a deciduous broadleaved forest on the Ebino Plateau, during the breeding seasons from 1997 to 2000.
Leiothrix foraged in a lower vegetational layer with bamboo, intermediate in height between the foraging levels of the Japanese Bush Warbler Cettia diphone and various Parus species. Foraging height, extent of foraging on deciduous trees and foraging technique were major factors best distinguishing Leiothrix from native species. Segregation of foraging niche was distinct and no apparent niche shift, due to invasion of the new species, was detected. Aerial insects tended to be more abundant just above bamboo, mainly about one meter above the canopy, than above bare ground. Thus, jumping, a specific technique used by Leiothrix, is effective for capturing aerial insects or agile invertebrates resting on leaves and twigs. Aerial insects were found to be abundant in the foraging space preferred by Leiothrix. Gleaning and hanging, techniques mainly used by native species, are suitable for capturing prey of low mobility such as Lepidoptera larvae. Probably due to morphological constraints, Parus spp. and Japanese Bush Warblers seldom foraged by jumping, indicating that they exploit quite different food resources from those utilized by Leiothrix despite their foraging spaces overlapping to some extent.
In the deciduous broadleaved forests of Kyushu, an avian guild of foraging aerial insects in intermediate and lower layers of the forests is poor. Such a community may be subject to the successful invasion of the Red-billed Leiothrix into native forests.

Unno A
Tree species preferences of insectivorous birds in a Japanese deciduous forest: the effect of different foraging techniques and seasonal change of food resources.

I examined the effects of arthropod abundance and of bird foraging techniques on the tree species preferences of seven insectivorous bird species in a temperate deciduous forest. It is hypothesized that bird species with a wide range of foraging techniques respond more flexibly to the spatial distribution and seasonal change of prey than those with specialized foraging techniques. This hypothesis was supported by the fact that tits, bird species with a wide range of foraging techniques, changed their techniques when foraging in tree species with different foliage structures. They also used various tree species in late summer when food requirements increased owing to the addition of nestlings and fledglings. Bird species with a narrow range of foraging techniques, such as flycatchers and white-eyes, did not change their techniques among tree species and had strong tree species preferences in all research periods.