Changes in avifauna diversity for over 21 years at the Yokohama Nature Sanctuary, central Japan

Abstract

From 1986-2006 data from line transect surveys was analyzed as a way of determining the effects of habitat management of the breeding and wintering avifauna at the Yokohama Nature Sanctuary (YNS, area: 45ha) which has typical secondary forests of central Japan. We used data collected from yearly changes in avifauna species and numbers during the breeding season (April-June) and wintering season (Jan-Feb). Generalized linear mixed models were used for the analysis. A total of 95 species, including 7 species listed in the Kanazawa Prefecture Red Data book as EN, VU or NT and 7 species that primarily breed in large-sized forests were observed. When divided into seasonal movements, there were 27 residential, 7 summer visitor and 28 winter visitors recorded. Analysis results showed that over 20 years species richness increased, especially in breeding birds. Also the number of recorded species greatly increased as the course went uphill. From these results, we have come to 2 conclusions 1) It is possible to maintain avifauna diversity of YNS, especially for breeding birds. 2) Survey methods, especially survey course direction, has a strong influence on the number of recorded species. If differences in transect methods are ignored, the yearly changes in species numbers at YNS may be misunderstood.