It is clear that mowing to Pleioblastus chino contributes to the plant variety diversity in herbaceous layer. But, the research of the influence that reaping undergrowth gives to the animal kind is not enough. Then, this research aimed to clarify the influence of weeding in the under to birds. I selected the broad-leaved deciduous forest four places in Yokohama city which is 10ha or more. About one set the investigation district of 20~30m to the green tract of land by 11 places. The investigation district was set for the height of Pleioblastus chino to change gradually from Cutting every year area to Leaving area of 11 years or more. The research did vegetation investigation and birds investigation. Birds' appearance layer did not have bias in the number of seeds at the breeding period, and there were a lot of numbers of individuals in the upper layer. The number of seeds and the number of individuals were biased to the lower layer in wintering term. As for the relation between birds' distribution and the height of Pleioblastus chino, it was suggested that the living condition become excellent when the height of Pleioblastus chino became 50cm or more.
