Introduction of exotic birds into Japan has been increasing. So far, forty-three species have bred at least once here. Most of these exotic species were imported as caged birds and entered the natural environments either accidentally or deliberately. Dominant taxa are Psittacidae, Passeridae (Estrildinae and Ploceinae) and Sturnidae. Most of the exotic birds are established in habitats disturbed by humans such as reed beds, riparian grasslands, croplands, and towns. Exceptions are Timaliidae such as the Red-billed Leiothrix Leiothrix lutea and the Melodious Laughing Thrush Garrulax canorus, which have invaded indigenous forests. Although most species are restricted to small particular areas, the Red-billed Leiothrix has been rapidly increasing and expanding its geographical range. Serious adverse influences by introduced birds on local ecosystems, biota and human economic resources have not been pronounced yet in Japan, except for crop damage or other economic damages by the Feral Pigeon Columba livia and Light-vented Bulbul Pycnonotus sinensis formosae. Therefore, public concern about avian introduction is low in Japan. Strict control of import of exotic birds, a registration system of caged birds, eradication and management of established exotic birds, and more research and public education about avian introduction are necessary.
The Melodious Laughing Thrush Garrulax canorus is an introduced species in Japan, and it has been recorded in the wild since the 1980s. The distribution of this species was estimated based on questionnaires. Four populations of this species have been confirmed in the western Kanto, northern Kyushu, southern Tohoku and Nagano Prefecture. There is a possibility that the expansion of this species is limited by elevational conditions and snowfall. Nevertheless, the distribution is still expanding. Therefore, it is necessary, as soon as possible, to assess the effect of the Melodious Laughing Thrush on the native birds.
Exotic Red-billed Leiothrix Leiothrix lutea numbers have increased in southern, western and central part of Japan since the early 1980's. Unlike most naturalized birds, this species mainly breeds in natural deciduous forests. We researched the breeding bird density in a deciduous forest on Mt. Tsukuba (877 m), a major breeding area of leiothrix in central Japan, in 1994 and 1995. Leiothrix bred at very high density (350-400 pairs per 100 ha) and was the most dominant species in both years. In 1995, six complete nests were found in a 1 ha area. In spite of the high breeding density of leiothrix, native avifauna showed species diversity, total breeding density and total biomass, similar to other Japanese deciduous forests. Therefore, we suggest that leiothrix have invaded Mt. Tsukuba without severe competition with native bird species.
Exotic bird introductions to Australia, New Zealand and surrounding islands, have been aggregated into one of the best documented and most completely analysed datasets available on biological invasions. Of the >242 species introduced by Europeans to Australasia during the 18th-20th centuries, at least 32% established long-term viable populations. A review of the literature reveals the most robust predictors of introduction success to be total number of individuals liberated, and the number of separate attempts at introduction. Using generalized linear modelling on a combined regional dataset, I confirm this result, and demonstrate that together these two characteristics of historical introductions correctly explains the observed outcome in 89.3% of cases in Australasia. Further, I show that a simple stochastic population dynamics model, derived for a sub-set of 44 species from entirely independent longterm studies, is also able to achieve a high degree of predictive success (83%). Finally, a suite of meta-analyses have shown the strongest life history and environmental correlates of introduction success to be large body size, low propensity to migrate, climatically matched habitats across the native and invasive geographical range, sexually monochromatic plumage, dietary generalism, and greater behavioural flexibility. The collective results of these analyses on Australasian introductions provide a potentially powerful framework for predicting the probable outcomes of future bird invasions worldwide.
The natural vegetation of Hong Kong is tropical evergreen forest, but this was almost entirely cleared by people before the eighteenth century. This clearance must have had a major impact on the bird community and undoubtedly caused the disappearance of all forest-dependant species, but these changes are undocumented. The documented history of Hong Kong’s avifauna begins following British colonization in 1860 and parallels a process of progressive restoration of forests, at least in the uplands. At least nine bird species that were present in Hong Kong in 1860 are dependant upon anthropogenic habitats and are therefore considered to have invaded before colonial times. Subsequently 41 species (30% of the breeding avifauna) have colonized. Of these, 22 species are believed to have spread unaided from southern China, while the remaining 19 species are considered to have been introduced by people from sources both within and beyond the region. Unlike the pattern of documented bird invasions elsewhere in Southeast Asia, most of these recent invaders are forest species, reflecting the recent pattern of habitat change. The possible ecological impacts of these invaders (both natural and human-assisted) are reviewed, but they are largely unknown. Hong Kong may provide a model for the evolution of bird communities elsewhere in the region if current patterns of deforestation are permitted to continue.
Invasive birds can have serious impacts on native biodiversity, native ecosystems and humans. However, there is a dearth of literature on the status and effects of invasive birds in Southeast Asia. We review the current available information on the invasive bird species in Southeast Asia, first by discussing characteristics that likely make invasive bird species successful and second by reviewing the impacts of the invasive bird species on Southeast Asian economy and biodiversity. We end by discussing the strengths and weaknesses, as well as the applicability of different management options.
Carrion Crows Corvus corone often establish spring roosts even during the breeding season. To examine whether the individuals roosting in spring are juveniles with immature reproductive organs, we compared the body size, sexual organs, and plumage of 150 roosting and 35 breeding individuals collected in the Joetsu region, Niigata, Japan, between 20 April and 9 May 1992. In both sexes, roosting individuals had significantly lighter bodies, and shorter wings and tails than breeding individuals. Roosting males had significantly lighter and shorter testes, and a lower testes/body percentage than breeding males. All 15 breeding males and 17 of 70 roosting males (24.3%) had mature testes, while 53 of 70 roosting males (75.7%) had immature testes. Roosting females had significantly lighter ovaries and a lower ovary/body percentage than breeding females. All 20 breeding females and 19 of 80 roosting females (23.8%) had long, enlarged oviducts, while 61 roosting females (76.2%) had undeveloped oviducts. Based on plumage characteristics, we estimated that 112 of the 150 roosting crows (74.7%) were juveniles. The reproductive organs of 108 of the 112 juveniles (96.4%) and 6 of 38 adults (15.8%) were immature. These results suggest that the spring roost consisted mainly of juveniles with immature reproductive organs. Thirty-six roosting individuals had mature reproductive organs. We considered them to be either territorial adults that had attempted to breed near the roost but failed, or sexually mature non-territorial males.
We examined habitat use and foraging behavior of male Black-and-white Warblers (Mniotilta varia) in fragments (2-140 ha) of mature forest dominated by trembling aspen (Populus tremuloides) and a similar contiguous forest (> 1000 ha) in central Alberta, Canada. Vegetation structure and composition differed significantly between occupied and unoccupied fragments, and between plots within and outside territories in occupied fragments. Territories in fragments were characterized by a high abundance of willow (Salix spp.), which was the primary foraging site for males in this habitat. Territories in contiguous forest differed significantly in vegetation structure from territories in fragments, and were characterized by a high abundance of trembling aspen trees, which served as the primary forest foraging site. The use of foraging substrates and foraging methods did not differ between individuals in fragments versus contiguous forest. In the boreal mixedwood ecoregion, the Black-and-white Warbler appears flexible in its habitat use.
We developed a new method to estimate the auditory abilities of animals using responses elicited by the presentation of auditory stimuli, without restraining or training the subjects. Using this method, we examined the hearing ranges of four raptors (a Mountain Hawk-eagle Spizaetus nipalensis, Northern Goshawk Accipiter gentilis, Common Buzzard Buteo buteo, and Grey-faced Buzzard-eagle Butastur indicus) kept in Ueno Zoo, in Japan, by presenting pure tones and white noise at two sound-pressure levels. Unconditioned responses, such as pupillary dilation and physical movements, were observed in all subjects. We then presented paired video clips of the raptors, with and without auditory stimuli, to human assayers, who were asked which clip contained the auditory stimulus. The accuracy of the human perceptual assay (HPA) suggested that the Mountain Hawk-eagle and Northern Goshawk hear frequencies from 1 to 5.7 kHz best, which is comparable to the results of an experiment with an American Kestrel Falco sparverius and European Sparrowhawks Accipiter nisus. The assayers reported that they used movements of the neck, head, and eyes, and changes in the pupils of the raptors as critical cues. Our method reliably reflected the hearing ranges of the raptors, and should be helpful for estimating the auditory capabilities of rare animals, such as the Mountain Hawk-eagle studied here.