Effects of Urban forest patch characteristics on Bird community Assemblage in Kathmandu Valley

Abstract

Urbanization poses a significant threat to biodiversity, leading to habitat fragmentation and ecological imbalance. In fast growing cities like Kathmandu, the effect of rapid urbanization had serious impact on biodiversity. In this study the effect of urban forest patch characteristics on bird community structure of Kathmandu Valley, Nepal was investigated. A total of 92 of point counts in 15 patches were surveyed for birds using the point count method. Bird species richness and abundance as the response variable were analyzed using 23 explanatory variables (distance to source forest, area, perimeter, round, Shape Index, interior to edge (IE) ratio, urban strata, monkey presence (high, low, medium), place (15 forest patch), habitat (edge or not), season (summer and winter), cloud cover, wind, humid, precipitation, canopy cover, percentage of pine, and vegetation ground attributes (percentage of tree, bush, soil, grass, and litter; tree height). Generalized linear model was used to analyze the relationship among forest patch characteristics and bird species richness and abundance. Winter season showed negative relations to both bird species richness and abundance. Vegetation covers such as tree percentage, bare soil, litter have significant relation to both species’ richness and abundance. Forest patch area showed a positive relation to species richness, with larger patches supporting higher species numbers. However, the patch shape index showed a negative impact on species richness suggested by a lower species richness in irregular shaped patch containing higher shape index. Patches closer to the source forest support higher individuals of birds while the patches far from source have low species abundance as they are more isolated. This study found that within the urban green patches in Kathmandu Valley, the forest patches that are closest to the city center and that are most disturbed have the lowest Shannon diversity index. The results suggested that urban forest patches that were far from the disturbed city center and with diverse habitatssupported higher species richness of birds. Within the context of conservation, promoting these urban green patches in a fast-growing city should be a priority for urban planners and conservationists.