I reviewed researches addressing avian life history evolution in the tropics, with special reference to the latest knowledge collected in Australian monsoon tropics. In the tropics, a large body of empirical data and comparative studies in which phylogeny and ecological conditions such as nesting habitat were controlled, have demonstrated that clutch size is smaller and survival of adult birds is higher than in north temperate areas. However, no such significant differences have been detected in the nest predation rate, incubation period, fledging period, number of broods per season. Insufficient data exists regarding the provisioning rate, food size and total amount of foods for chicks. In Australian monsoon tropics, which are characterized by a small seasonal change in temperature and by the distinct alteration of six-month dry season and wet season, the seasonal variation of food abundance, mainly invertebrates and nectar, is smaller than in northern temperate areas. Although breeding occurs in every month throughout avian communities, there are diverged patterns of breeding seasons among species. Most life history traits show a similar tendency to those of birds in other tropical areas. Low adult mortality and low population turnover cause the delayed first breeding in young and delayed natal dispersal, which is a causal factor for the cooperative breeding system that prevails among Australian bird species. Frequent wildfires adversely influence the breeding of grass-nesting species. In contrast, some adaptation to fires is evident, e.g., enhanced reproductive success by virtue of new food resources and foraging habitats created by fires or behaviours in lessening the damage of fires.
Male Great Bowerbirds Chlamydera nuchalis build a bower and pile decorations around it for courtship display. We tested the effect of the bower structure and amounts of decorations on the mating success of owner males in a population of C. n. nuchalis near Darwin, Northern Territory, Australia. We collected data on measurements of bowers and mating success of individual owner males for 16 and 14 bowers in 2005 and 2006, respectively. We used five variables (avenue length, avenue width, wall thickness, bower height and degree of asymmetry) corresponding to the bower structure, and two variables (coverage (%) of green decorations and that of all decorations) corresponding to amounts of decorations as explanatory variables. An analysis of the generalized linear mixed model and model selection revealed that avenue length and wall thickness affected mating success positively, and that of avenue width, negatively. Avenue length and wall thickness correspond to the size of the bower, which suggests that a larger bower provides females with better protection from a vigorous male's display. A long and narrow avenue may provide a refuge for females from the harassment by an owner male. No variables corresponding to decorations were important for the mating success.
Male courtship displays commonly involve multiple sexual signals. While there has been considerable interest in female choice for male multiple signals, few studies have investigated how these signals interact. We analyzed courtship behaviours of male Great Bowerbirds Chlamydera nuchalis, which include both acoustical elements, including ticking sounds of three types (SS, MS and LS), and locomotive elements, including dancing around the bower. Our results show that the ticking sounds played an important role in female choice. Males that uttered more LS sounds (louder and longer than the other two types) attracted more females, which suggests that intense display enhances mating success. In addition, males uttering more LS type calls had a larger bower, which suggests that a large bower provides females a safe protection against male's vigorous display and that the male can perform display more intensely. These results show that the multiple signals interacted with each other.
We conducted a study to clarify the impact of bush fires on the structure of non-breeding flocks of the Red-backed Fairy-wren Malurus melanocephalus cruentatus in the Australian monsoon tropics. Overall, the mean group size was large in the mid dry season, becoming smaller with the progress of season. Large groups occurred at burnt sites, while at unburnt sites group size was smaller owing to a higher proportion of pair-sized groups. Bush fire destroyed habitat and forced resident birds to emigrate. Conversely, unburnt sites were used as a refuge during fires. However, in the non-breeding season, such stable habitats were occupied by stable and small-sized groups and were already saturated. Therefore, individuals that immigrated into these habitats during fires were forced to emigrate again. After a fire, many birds invaded burnt sites from the surrounding area and aggregated in large but unstable flocks that consequently diminished due to the individual separation of young males just before the breeding season. Bush fires resulted in the reorganisation of groups and re-establishment of territory.
Nest predation is high in mangals (mangrove communities) of the Australian monsoon tropics. The Large-billed Gerygone Gerygone magnirostris and Mangrove Gerygone G. levigaster are warbler-like birds that build domed nests, which are very different from each other in size, form and colour. Large-billed Gerygone forages and builds nests along tidal creeks where vegetation is tall and dense, whereas Mangrove Gerygone primarily nests in shrubs around the edges of bare salt flats and forages in both habitats. Using artificial nests that mimicked those of the two species, we tested whether differences in nest appearance, including form and colour, were adaptations to avoid nest predation. Artificial Mangrove Gerygone nests in their main nesting habitat were predated less frequently than those on tidal creeks, whereas predation rates on artificial Large-billed Gerygone nests did not differ between habitats. Our results suggest that Mangrove Gerygone nests are built in the primary breeding habitat to avoid nest predators. In addition, we identified a nest predator, the Yellow Oriole Oriolus flavocinctus.
We reported characteristics of external morphology and DNA sequence from the carcass of a large-sized gull with yellow legs recovered at Teuri Island, Hokkaido, Japan. According to Olsen & Larsson (2003), based on the tone of the upperwings and mantle and the pattern of the primary tips the carcass sample was identified as Larus heuglini, but could not be identified at the subspecies level. Sequence variation in the cytochrome b and control region gene of the carcass sample agreed with common types of closely-related taxa (fuscus, heuglini, barabensis, or taimyrensis). Our study underscored the difficulty in identifying large white-headed gulls accurately even when based on quantitative data such as those obtained from carcass samples or DNA sequences. Further quantitative studies on inter- and intra-population variations in external morphology of birds at each breeding site are needed.
A total of 15 individuals of the Ryukyu Robin Erithacus komadori were observed in the foothills of Yakushima Island every August from 2006 to 2008. The Ryukyu Robin had been rarely seen in Yakushima Island and this is the first authentic report with photographs.
The song of the Japanese Night Heron Gorsachius goisagi has long been known from its distinctive low, carrying call which sounds like ‘ivoh—’. The actual status of the song, however, has little been studied. The author conducted a comparative survey of the song at song posts and during the breeding period at breeding sites in Tokyo in 2008, using a digital voice recorder and a digital video camera to record the song. The study documented the song at song posts during night for 10 consecutive nights. The song usually continued from sunset until next morning and in an extreme case, lasted for 10 hours. However, once a breeding pair was established, they immediately stopped singing and thereafter, the song was not observed during the breeding period regardless of day or night. Results of this study suggest that the singing activity of the Japanese Night Herons is done intensively at night for a short period from immediately after their arrival in Japan up until pair formation occurs, and that thereafter, no singing occurs either during the daytime or at night. The Japanese Night Heron derived its common name from the belief that it was a nocturnal species. This might be because male birds sing intensively only at night. However, the results of the present and previous studies revealed that this species to forage exclusively during the daytime both in the breeding and non-breeding seasons. This species can therefore be considered diurnal, except for short periods.
The Japanese Marsh Warbler Locustella pryeri is an endangered species that has two large breeding populations (Hotoke-numa and Tone River) in Japan. These are thought to comprise the same subspecies, although the morphological and genetic data for the two populations have never been compared. Recent body measurements suggest that these two populations may differ in wing length. In this study, we compared the plumage colorations of these two populations using photospectrometric measurement, and found them to have similar reflectance patterns of plumage coloration. Although we found no difference in colours between the two populations, future work should concentrate on describing and comparing the two populations using additional colour data.
A Thick-billed Murre Uria lomvia was observed foraging at Hiura fishing port, northern Japan (41°43′N, 141°03′E), around midnight on May 17 and 18, 2010. The sea surface, where the murre dived and foraged, was brightly illuminated by an artificial light. Several taxa of zooplankton including amphipods, a known dietary item of murres, were swarming below the sea surface. The murre foraged near the artificial light on a dark night, which might possibly be related to the abundance of prey, namely zooplankton, and/or to the presence of sufficient light to search for food.
In March 2009 Mr. Tsutomu Fujimoto donated to the Yamashina Institute for Ornithology a collection of bird skins comprised of 101 specimens of 35 species. Many of the specimens were collected from Tatsuno-shi, Hyogo Prefecture.