ORNITHOLOGICAL Science
Volume 1 Number 1 January 2002
Loyn RH
Patterns of ecological segregation
among forest and woodland birds in south-eastern Australia.
Much information has been gathered on birds of eucalypt forests
and woodlands in south-eastern Australia. This was examined to
assess some of the mechanisms of ecological segregation that may
apply. A database was constructed of 209 species pairs (148 species
from 48 genera). Most patterns resemble those reported overseas,
with habitat and range featuring as major segregating mechanisms.
Use of different strata and substrates was the dominant primary
mechanism allowing use of identical space by congeners. Mechanisms
such as specific food preferences, migration and choice of nest
sites contributed but rarely as primary factors. One species pair
appears to show no ecological segregation, despite co-existence
in varying proportions over a large geographical range. Indiscriminate
interspecific aggression is used by some species to maintain high
levels of resources for themselves, in environments that can sustain
such resources throughout the year. Communal breeding is a feature
of those species. Implications for conservation are discussed.
Recher HF, Davis WE Jr & Calver
MC
Comparative foraging ecology
of five species of ground-pouncing birds in western Australian
woodlands with comments on species decline.
In this paper, we compare the foraging ecology of five Australian
robins (Petroica multicolor, P. goodenovi, Eopsaltria griseogularis,
Microeca fascinans, and Melanodryas cucullata) in woodlands of
Western Australia. Australian robins are insectivorous and obtain
the greatest proportion of their prey by pouncing from a perch
to the ground. Data were collected at three different sites in
eucalypt (Eucalyptus) woodland and two sites in acacia (Acacia)
woodland. The species differed in habitat, structure of the ground
substrates where prey were taken, proportion of foraging manoeuvres
used, height of foraging perches and prey-attack distances, though
there were broad overlaps in all foraging dimensions. Within a
site, species were more similar to each other in their foraging
behaviour and selection of foraging substrates than they were
to conspecific individuals occurring elsewhere. This indicates
that potential foraging behaviours were very broad, and their
expression is determined by the characteristics of the habitat
and available prey. At all sites, robins took prey from ground
substrates characterised by a mosaic of bare soil, low ground
vegetation, and litter. The smallest species, P. goodenovi, used
lower perches than the other robins and probably searched for
small prey which it located at short distances. P. goodenovi had
the widest distribution and was the most abundant of the species
studied. The implications of these findings for the conservation
of ground-foraging birds in Australia are discussed.
Moenkkoenen M & Forsman JT
Heterospecific attraction
among forest birds: a review.
In this paper we review the evidence for a habitat selection
process where colonizing individuals use other species presence
as cues to profitable breeding sites. Our experimental studies
in Fennoscandia and North America have shown that density and
species richness of migrant birds breeding in the forests respond
positively to experimentally augmented titmice densities. We used
analytical modeling to analyze ecological conditions, which may
favor a habitat selection process where later arriving individuals
(colonists) use the presence of earlier established species (residents)
as a cue to profitable breeding sites. We compared the fitness
of two colonist strategies: colonists could either directly sample
the relative quality of the patches (termed samplers) or, alternatively,
they could also use residents as a cue of patch quality (cue-users).
Model results suggested that cue-using strategy is more beneficial
in most ecological conditions and that this may result in heterospecific
attraction. Further field experiments showed that migrant individuals
selected nest sites at close vicinity of nesting titmice, and
bred earlier and reproduced better. We conclude that heterospecific
attraction may be a common and widespread process among forest
birds particularly in seasonal environments.
Seki S & Sato T
The effect of a typhoon
on the flocking and foraging behavior of tits.
A typhoon, that struck Kyushu, the southernmost of the four
main islands of Japan, in September 1999, causing extensive wind
damage to forests, was found to have affected the flocking and
foraging behavior of Varied Parus varius and Great Tits P. major.
After the typhoon had passed, the tits tended to participate in
mixed-species flocks and preferred to forage in the lower parts,
rather than in the upper parts, of the trees. Also the proportion
of plant products in the diet of the Varied Tit was reduced. The
population and average flock size of the tits, however, remained
stable even after the typhoon. The abundance of plant products
as food resources remained unchanged despite severe damage to
the trees, but the vegetation cover was reduced, which probably
increased the predation risk. The increase of mixed-species flocking
may have resulted from the increased risk of predation; mixed-species
flocking is thought to increase vigilance and foraging efficiency
while not increasing intraspecific competition. Changes in diet
and preferred foraging sites were also consistent with the increased
predation risk hypothesis. We conclude that the changes in foraging
and flocking behavior after the typhoon were mainly due to the
increased predation risk caused by the reduced vegetation cover.
Murakami M
Foraging mode shifts of
four insectivorous bird species under temporally varying resource
distribution in a Japanese deciduous forest.
Temporal changes in the foraging habitat of four forest bird
species and the distribution pattern of arthropod populations
were investigated. The abundance and distribution of arthropods
changed drastically with the season within the forest. Lepidoptera
larvae were most abundant in the canopy in the first three weeks
after budbreak; their numbers decreased rapidly during mid-June.
In contrast, on the forest floor, the larvae were abundant from
early to late June. The foraging height of the Narcissus Flycatcher
Ficedula narcissina changed in parallel with the distribution
pattern of Lepidoptera larvae. Three other species, the Great
Tit Parus major, Marsh Tit P. palustris, and Eastern Crowned Warbler
Phylloscopus coronatus, however, did not change their foraging
heights; they continued to forage in the canopy. These differences
are probably due to the greater preference of the flycatcher for
Lepidoptera larvae compared with the other three species. The
three other species switched from feeding on Lepidoptera larvae
to spiders or other arthropods in mid June, when the number of
Lepidoptera larvae decreased in the canopy. The results of this
study suggest that the abundance and distribution of arthropods
and differences in foraging tactics among bird species considerably
affect avian foraging habitat. The foraging behavior of three
species of forest birds revealed species-specific responses to
spatio-temporal fluctuations in the distribution of resources.
Mizutani M & Hijii N
The effects of arthropod
abundance and size on the nestling diet of two Parus species.
Feeding habits of Parus major and P. varius inhabiting coniferous
plantations of Cryptomeria japonica and Larix kaempferi, each
containing a small area of deciduous broad-leaved trees, were
analyzed in relation to the abundance and size distribution of
arthropods. In a C. japonica-dominated (CJ) area, C. japonica
trees were mainly used by P. major only, while deciduous broad-leaved
trees were used by both Parus species. In a L. kaempferi-dominated
(LK) area, both Parus species used L. kaempferi trees and deciduous
broad-leaved trees. The composition of nestling diets differed
between Parus species. For prey size, the difference in the breadth
was smaller and the overlap was larger between areas than between
species. These results suggest that each Parus species preferred
a specific size class of prey. That is, the single-prey loader
P. major preferred large prey, whereas the multiple-prey loader
P. varius preferred small prey. The abundance and size distribution
of arthropods greatly differed among foraging microhabitats. Both
Parus species selectively used foraging microhabitats according
to their prey-size preference.
Hino T, Unno A & Nakano S
Prey distribution and foraging
preference for tits.
We examined the abundance and distribution of prey in four different
height strata and eight tree species in a temperate forest, and
analyzed the influence on foraging preference by three breeding
tit (Parus) species. Densities of arthropod prey for tits in canopy
foliage varied with tree species but not with height. Most of
them were Lepidoptera larvae. Also, interspecific differences
in choice of foraging substrate were found between tree species
but not in height. These results demonstrate that tree species
composition is a more important habitat factor than foliage height
profile for coexistence of different tit species in forests. We
examined four different measures of prey abundance to find how
tits chose tree species. The largest species, the Great Tit P.
major, preferred the tree species with high total biomass, and
the intermediate-sized Willow Tit P. montanus preferred those
with high density per leaf area. Concentrated searching for prey
on a few tree species with high total biomass may be a useful
strategy for inflexible perch-gleaners such as P. major, and finer-scale
searching on each leaf may be more practical for agile foragers
such as P. montanus which often hang-glean to reach less accessible
food. In spite of these differences, both species gained benefits
from choosing the tree species on which they foraged most efficiently.
In contrast, the smallest species, the Coal Tit P. ater, frequently
foraged on food-poor tree species. Of the three tit species, P.
ater was the most generalized forager, using diverse techniques
on a variety of tree species and specializing at capturing small
prey quickly. These foraging patterns may make it possible for
the smallest species to coexist with the other tit species.
Sodhi NS
The effects of food-supply
on Southeast Asian forest birds.
Southeast Asian forests are being lost at an alarming rate.
This unprecedented deforestation is resulting in avifauna losses.
Despite this, Southeast Asian avifauna remains poorly studied.
A few studies measured the food-supply and correlated it with
the Southeast Asian forest bird ecology. These correlative studies
(qualitative as well as quantitative) show that food-supply can
affect the bird diversity, abundance/density, breeding ecology,
body condition, ranging behaviour and/or flocking behaviour. However,
there has been no experimental study conducted to determine the
effects of food-supply on the forest bird ecology. In this geographic
area, exciting research avenues remain available to study the
avian feeding ecology and to explore a relationship between food-supply
and forest bird ecology. Descriptive, correlative as well as experimental
data on these aspects are required to enhance the knowledge of
avian ecology as well as for avian conservation purposes.
Yamagishi S, Asai S, Eguchi K &
Wada M
Spotted-throat individuals
of the Rufous Vanga Schetba rufa are yearling males and
presumably sterile.
The Rufous Vanga Schetba rufa is endemic to Madagascar and lives
in one-female groups. During the 1994 Ð1999 breeding seasons, a
total of 294 nestlings were banded. Among these nestlings, 51
stayed within the study area as spotted-throat individuals. In
the next breeding seasons, 35 of 45 spotted-throat individuals
were subsequently observed as black-throated males, and once they
became black-throated males, these individuals never reverted
to the previous spotted-throat pattern. In contrast, 30 banded
nestlings were recovered as yearling females with white throats,
and the female Õs color pattern never changed thereafter. All the
spotted-throat males were helpers or floaters. All the males of
one group consisting of an adult male with a black throat and
two males with spotted throats were captured and sacrificed humanely.
The testes were dissected from each specimen and were histologically
examined. The testes of the spotted-throat males contained only
spermatogonia, and no spermatids or spermatozoa were present.
In contrast, the testes of the black-throated male were well-developed
and contained enlarged seminiferous tubules with lumen, where
numerous spermatozoa were evident. Considering these facts, spotted-throat
males of this species are assumed to be sterile. We suggest that,
due to their underdeveloped testes, the spotted-throat males (one-year-old
males) of the Rufous Vanga are physically incapable of breeding.
Amano HE & Eguchi K
Nest-site selection of the
Red-billed Leiothrix and Japanese Bush Warbler in Japan.
The Red-billed Leiothrix Leiothrix lutea has been introduced
from China and is rapidly increasing in deciduous broad-leaved
forests of Japan. We studied nest-site characteristics and nest-site
selection of this species and the Japanese Bush Warbler Cettia
diphone, a sympatric native species, in southwestern Japan. Both
species placed nests exclusively in bamboo thickets and on bamboo
stalks. The Red-billed Leiothrix built pendulous nests in the
canopy of high concealment. The Japanese Bush Warbler placed nests
on the crossing of bamboo stems and selected places of high stem
density. The Japanese Bush Warblers placed nests in denser vegetation
than the Red-billed Leiothrix. The segregation of nesting microhabitat
was also evident in both species to coexist in bamboo thickets.
Existence of few inhabitants in bamboo thickets may contribute
to the invasion success of the Red-billed Leiothrix.