Volume 1 Number 2 September 2002
Breeding bird community and mixed-species flocking in a deciduous
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
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
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.
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.