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The effects of trampling and burrowing by streaked shearwaters were studied on the Persea thunbergii forest in Kanmurijima Is. The vegetation data were analysed using both the phytosociological tabulation method and principal component analysis (PCA). The vegetation ordination on the first axis reflected the environmental gradient from light to heavy disturbance by the streaked shearwater, and the vegetation ordination on the second axis represented the gradient from the latter phase of forest succession to retrogressive succession. The position of the three vegetation groups in the ordination diagram successfully explained the relation between the habitat and the species composition. The disturbance caused by activities of the streaked shearwater such as burrowing and trampling causes a decrease of species, especially character species of Camellietea japonicae, and also causes retrogressive succession: patches of Mallotus japonicus develop and many heliophytes occur.

Machilus thunbergii forests were studied in Kanmurijima Island, Kyoto Pref., to clarify the influence of disturbance by birds' nesting and streaking on the community structure of the forest. Density of nests was negatively correlated with the number of plant species and individuals, the skewness of frequency distribution of height and DBH, Shannon H' and the relative basal area of Aucuba japonica, respectively. Species composition, species diversity index, dominance-diversity curves, skewness of height distribution, crown projection diagrams and other ecological characteristics showed that the disturbance by birds resulted in poor vegetation and the development of simple stratification. The species diversity became slightly higher as the aboveground biomass increased. In these forests Mallotus japonicus very often filled up gaps of canopy trees, and seedlings and saplings of Machilus thunbergii were growing around patches of Carex matsumurae and some herbs as stable spots for germination on the forest floor.