Effectiveness of nature reserves for bird conservation in urban parks in Tokyo

Abstract

In some urban parks in Tokyo, semi-natural habitat patches are maintained as nature reserves for birds, called bird sanctuaries. Bird censuses and vegetation surveys were conducted in eight urban parks in Tokyo from December 2015 to July 2016 to determine the effectiveness of bird sanctuaries on avian species composition. The relationship between avian species composition and environmental conditions was analyzed by partial redundancy analysis (partial RDA) using vegetation variables, number of visitors, presence or absence of reserves within the same park, area of wooded parts, and normalized difference vegetation index (NDVI) in the surrounding area. The results of the partial RDA are as follows: (1) Area, lower vegetation cover, higher vegetation cover, tree species composition obtained from detrended correspondence analysis (DCA) on vegetation survey data, and NDVI in the surrounding area were considered as covariates and explained 17.4–33.6% of the total variation in bird species composition, (2) The presence or absence of sanctuary significantly explained bird species compositional variation regardless of season, indicating that the sanctuaries were beneficial for urban avoider species not only in the sanctuaries but also in the surrounding wooded area, and (3) Tree coverage within a 100 m range and leaf litter coverage also influenced avian species composition. We concluded that bird sanctuaries and other nature reserves can be beneficial to bird conservation, even within Tokyo. The positive effect of sanctuaries could be due to the limited influence of human presence and the developed vegetation within them. These reserves may play the role of core habitats within the studied urban parks.