Connectivity analyses of avifauna in urban areas

Abstract

Some resident birds widen their habitat ranges during the non-breeding season. Their wintering habitats may be determined not only by quality of habitats but also by their connectivity to source habitats. In this study, we extract some possible stepping-stone corridors and evaluate which corridors explain the presence/absence of four resident birds-the Bush Warbler, Long-tailed Tit, Varied Tit, and Masked Grosbeak-in possible wintering habitats in Kyoto City. Bird surveys were conducted in 18 woods (> 0.6 ha): almost all-potential breeding patches for these four species in the urban area of Kyoto. I assume the mountain forests around the city and patches in which each bird species was recorded during the breeding season to be their source habitats, and assess whether corridors connect their source and possible wintering habitats. A 15 × 15 m resolution vegetation cover ratio (VCR) map was derived from Terra/ASTER and Quick Bird images. We assumed the minimum VCR for stepping-stones to be 0.25 and created buffer zones from each stepping-stone at four distances: 50 m, 75 m, 100 m, and 125 m. Four types of corridors were extracted from the contiguous buffer zones. The maximum interval between stepping-stones was twice the distance of the created buffer. The maximum interval for suitable corridors evaluated by maximum Cohen's kappa, maximum overall prediction success, and minimum interval for which more than 80% of the actual wintering habitats connect to the source habitats were, respectively, 200m (kappa 0.25), 200-250 m (75% success), and 200m (89% connection) for the Bush Warbler; 100 m (0.12, 58%) and 150 m (80%) for the Long-tailed Tit; 100 m (1.0, 100%, 100%) for the Varied Tit; 100 m (0.29, 64%) and 250 m (100%) for the Masked Grosbeak. Though further analysis may be necessary, these results give us some indication regarding the size of the interval between stepping-stones necessary for planning ecological corridors. © 2007 Springer Netherlands.