We conducted a survey of biotic and abiotic factors correlated with waterbird assemblage composition in the Aspen Parkland, an endangered transitional zone between prairies and boreal forest, rich in waterbirds but poor in information relating avian distributions to features of aquatic habitats. We surveyed breeding aquatic bird species, plus invertebrates, fishes and limnological factors on 25 naturally eutrophic to hypertrophic lakes in Alberta, Canada. We observed 43 non-passerine species. Canonical Correspondence Analysis revealed two assemblage types: (a) a “grebe-gull” assemblage of gulls, grebes and waterfowl on hypertrophic lakes with small-bodied fishes and invertebrate assemblages of Diptera, Cladocera, Amphipoda and Glossiphoniidae, or (b) a “teal-shorebird” assemblage of ducks and shorebirds on eutrophic fishless lakes with invertebrate assemblages of Gastropoda, Erpobdellidae, Dytiscidae and Trichoptera. Lakes with “grebe-gull” assemblages were deeper and the presence of fish added to the resource base of these systems, perhaps contributing to greater species richness in “grebe-gull” lakes (x=12.5 species in presence of fishes, x=8.1 species in absence of fishes). Phytoplankton (chlorophyll-a) and nitrogen (TDN) concentrations were the most important limnological factors correlated with bird-assemblage composition, and may influence composition of invertebrate resources for birds on the two types of lakes. Our multivariate approach could be useful to managers for identifying key environmental factors associated with the successful management of multiple waterbird species in the Aspen Parkland.
Few studies have examined the relative importance of habitat loss and fragmentation caused by structurally complex matrices such as plantations. We examined the effects of the loss and fragmentation of the original deciduous habitat (secondary deciduous broadleaf forest) caused by a larch plantation matrix on bird occurrences in deciduous habitats in both the winter and breeding seasons in Chikuma Highland, Nagano prefecture, central Japan. Birds were counted using the plot-count method in 33 (winter) and 51 (breeding) deciduous habitats with a range of surrounding habitat loss and fragmentation at a 1600-m scale. Three species groups, for which larch plantations are likely to function as low-quality matrices, were analyzed. Effects of landscape structure were found only for flycatchers, which were negatively affected by habitat fragmentation. Flycatchers frequently occurred in habitats surrounded by elongated habitat patches in which between-patch distances were short. This effect was significant after the confounding effects of habitat structure were removed. Because habitat fragmentation was more important than habitat loss, the destruction of habitat connectivity, i.e., isolation and contraction of habitat patches, may not be compensated by the amount of habitat and may primarily be considered in low-contrast landscapes.
Breeding ecology of the endemic Velvet Asity Philepitta castanea was studied in the rainforests of Ranomafana, southeastern Madagascar, from October 1990 to January 1991 and Masoala Peninsula, northeastern Madagascar, from October 2000 to February 2001. All three pear-shaped nests discovered during our study were placed at the end of hanging branches (6–8 m above the ground) of Tambourissa spp. (Monimiaceae) and Cryptocarya spp. (Lauraceae). Two female-plumaged birds participated in nest building in Ranomafana, whereas at two nests studied in Masoala one adult black male and one female participated. In the two study areas, only one adult female was seen to incubate and to take care of the young. The nestling period lasted about 17 days; the young were fed by a female-plumaged bird with prepared fruits of Tambourissa spp. and Aphloya theaformis shrubs (in Ranomafana). Strongly marked sexual differences, non-similar sex roles and male territorial attendance with displays, show that P. castanea has a polygynous, lek mating system.
A goal of many resource selection studies is to identify those habitats selected by a species. However, favorability of a particular habitat feature is likely contingent on such factors as landscape composition, predation risk, and an individual's resource needs. Identifying causes of variability in habitat utilization may serve to increase our understanding of the functional aspects of a species' habitat ecology. The Common Hill Partridge Arborophila torqueola is a species that requires broadleaf forest, but whose populations have declined as a result of fragmentation of subtropical forest. While habitat conditions during the pairing season (March–April) are thought to be important for the Common Hill Partridge's survival and reproduction, information on habitat utilization during this period is limited. We investigated habitat utilization by Hill Partridges within Baiposhan Natural Reserve in the mountains of southwestern China. We used pointing dogs to locate Hill Partridges during the pairing seasons of 2004 and 2005, and measured habitat characteristics at 60 flush sites and 60 associated random sites (within 100 m of flush sites). We recorded information on terrain, vegetation traits and defoliation leaf layer. Hill Partridges mainly utilized sites within elevations of 2,400–2,900 m and with an east-facing slope of 28.6±2.9 degrees, close to water resources and roads. The utilized sites had greater tree cover, shrub cover and thicker defoliation layers than randomly available, whereas numbers of bamboo and bamboo cover were less at flush sites than at random sites. PCA indicated that concealment, food, terrain and water resources best explained the birds' habitat utilization. Forest management practices that reduce poaching, livestock and logging may benefit the Common Hill Partridge through raising habitat quality and availability. Based on habitat utilization patterns of the partridges, we discussed the difference of habitat between them and Sichuan Partridge A. rufipectus, and indicated that Common Hill Partridges in the reserve should be Common Hill Partridges rather than Sichuan Partridges.
The purpose of this study was to define the number and density of both retinal ganglion cells and the oil droplets of cone photoreceptor cells in the Tree Sparrow Passer montanus. Retinal whole-mount specimens were prepared and stained with 0.1% cresyl violet for the ganglion cell study, and fresh retinal samples were subjected to color microphotography for the oil droplet study. The mean total number of ganglion cells was estimated at approximately 1.6×106; with an average density of 18,539 /mm2. The density of the ganglion cells peaked in the area centralis, at 26,000 cells/mm2, and gradually decreased with retinal eccentricity. Small ganglion cells persisted in the highest density areas, whereas the largest soma sizes were found in the lowest density areas of the retina. Four types of different colored oil droplets—red, yellow, green and clear—were identified with an average density of 25,680 /mm2. Among the different colors, the green oil droplets showed a significantly higher density (12,247 /mm2). The central retina contained a significantly higher number of oil droplets, with a density of 50,731 /mm2, similar to the specialization of this area for ganglion cells. The density and size of the different colored oil droplets were inversely related across the regions of the retina, also similar to the pattern shown by the ganglion cells. Thus, the characteristic specializations of ganglion cells, especially peak density of central retina may contain the retinal fovea and the highest population of green oil droplets may be important to adjust the suitable light wavelength.
Most studies on avian vocal ontogenesis have focused on taxa exhibiting some kind of vocal learning. This study provides a detailed analysis of vocal processes through early and late ontogenesis in 17 chicks of the Red crowned Crane Grus japonensis, a species lacking vocal learning. Three basic structural classes: trills, PE-chirps and PS-chirps and their transitional forms are described. Trends in call parameter values are presented for 10 age classes in the course of a period from birth to 9.5 months. We discuss our vocal classification with those reported for other crane species, relate the revealed stages of vocal ontogenesis in the Red-crowned Crane to biologically relevant life stages in this species and advance a hypothesis for the proposed function of retaining high juvenile frequencies in adolescent cranes for a prolonged period, up to voice breaking (a rapid significant decrease in fundamental frequency). We conclude, that voice breaking is universal for both sexes and that the retained high call frequencies may represent an infantile characteristic, essential in evoking care from the parents towards the growing chick and may also act as a mechanism to reduce aggression from conspecifics.
Two models of mechanisms have been proposed to account for resource partitioning between species with overlapping niches, i.e., niche differentiation and competitive hierarchy. I examined branch-side uses by color-marked individuals of eight canopy-foraging species (Long-tailed Tit Aegithalos caudatus, Marsh Tit Parus palustris, Great Tit P. major, Eurasian Nuthatch Sitta europaea, Japanese Pygmy Woodpecker Dendrocopos kizuki, Great-spotted Woodpecker D. major, White-backed Woodpecker D. leucotos and Grey-headed Woodpecker Picus canus) in mixed-species flocks on artificial feeding trees for three years. The three tit species and the Nuthatch used the upper sides of branches most frequently whereas the four woodpecker species used the lateral sides of the branches most frequently, as expected from the niche differentiation model. Among the three tit species and among the four woodpecker species, small-subordinate species foraged on a wider range of branches than large-dominant species, as expected from the competitive hierarchy model. In addition, branch-side uses were compared between individuals, years, social situations and food abundance conditions for five species (Marsh and Great tits, Nuthatch, Japanese Pygmy and Great-spotted woodpeckers) that were abundant over one year. The Marsh Tit and the Japanese Pygmy Woodpecker changed branch-side uses when feeding with the Great Tit and the Great-spotted Woodpecker, respectively. Annual differences in branch-side use by the Marsh Tit was also related to frequency of hostile encounters with the Great Tit. Intraspecific differences in branch-side use were shown in subordinate species (Marsh Tit and Japanese Pygmy Woodpecker) but not in dominant species (Great Tit and Great-spotted Woodpecker). Such individual variability may be important in allowing subordinate species to reduce intraspecific competition when foraging in the same flock. The effect of food abundance on branch-side use was not demonstrated in this study.