A study on the influences by introduced birds on native birds.

引种鸟类的归化一直是世界范围内保护本地物种生物多样性的一个严重问题。在日本，虽然有不少外来鸟类建立了归化种群，但对这一问题的生态学研究却很少。在本研究中，我澄清了红嘴Leiothrix的生态学，这是最成功的引进物种之一，以及它对同域本地鸟类，特别是日本灌木莺的繁殖的影响。在森林鸟类群落中，细刺鸟的优势种数超过了林莺。只有这两种在矮竹丛中繁殖。林莺的巢大多位于茂密的竹林中，而毛刺莺的巢密度范围更广。栖地选择的普遍习惯是狮门数量迅速增加的原因之一。其繁殖季节远长于其他同域物种。这两个物种的繁殖成功率都很低，主要原因是杰伊和蛇的捕食。与以灌木为主要食材的林莺不同，拟莺主要以低层高大树木的树叶和细枝为食。拟蓟马与受薪种的觅食空间垂直范围重叠较大，但在水平方向上存在分离。由于占据了落叶阔叶林地上的矮竹丛、在林下觅食、繁殖季节长等空缺生态位，致使拟思门数量不断增加。石莺和林莺的栖息地被梅花鹿破坏了。随着生境破碎化的进展，有必要对这两种物种的种群动态进行监测。

Naturalisation of introduced birds has been a serious problem in the conservation of biodiversity of native species throughout the World, In Japan, although not a few species of exotic bird species have established naturalised populations, there have been few ecological studies on this problem. In this study, I clarified the ecology of the Red-billed Leiothrix, one of the most successful introduced species, and its influence on the breeding of sympatric native bird species, particularly the Japanese Bush Warbler.The Leiothrix was the most dominant species among the forest living bird community and outnumbered the Bush Warbler. Only these two species bred in the bush of dwarf bamboo. While most nests of the Bush Warbler were located in the habitats of dense bamboo bush, the Leiothrix nested in bushes of much wider range of density. The generalistic habit of habitat selection is one of the reasons for the Leiothrix to have been increasing the number rapidly.The breeding season of the Leiothrix was much longer than those of other sympatric species. The breeding success was very low in both species, a main cause being the predation by the Jay and snakes.The Leiothrix foraged mainly on leaves and twigs of tall trees in the lower layers of forests, segregating from the Bush Warbler foraging mainly in the bush. The overlap of vertical range of foraging space between the Leiothrix and paid species was large, but there was the horizontal segregation between them.The Leiothrix has been increasing because they occupied a vacant niche, i.e. bush of dwarf bamboo in the floor of the deciduous broadleaved forests, foraging in the lower layers of the forests and long breeding season. The habitats of the Leiothrix and Bush Warbler has been fragmented by the Sika deer. It is necessary to monitor the population dynamics of these two species with the progress of the habitat fragmentation.