Tree stand diameter and shrub cover are major determinants of bird abundance in urban sacred groves of Kathmandu Valley

Urbanization alters the structure and function of forests, with significant implications for biodiversity. Understanding the response of biodiversity entities to urbanization is vital for sustainable urban development. However, urban ecology has been poorly explored in the Global South, including Nepal, where urbanization is occurring at a faster pace than in other regions. Kathmandu is one of the most rapidly urbanizing cities, with forest patches primarily represented in sacred groves. However, our understanding of the response of avifauna to the forest structure of these groves is limited. This study explored the response of bird numbers to the forest structure. We used the standard point count method, laying seventy-two points randomly in nine sacred groves to carry out vegetation and avifaunal surveys. At each location, we counted the number of birds for five minutes. Additionally, we noted vegetation characteristics, including tree height; diameter, canopy cover, and shrub cover at each point. The relationship between bird abundance and vegetation structure was explored using a negative binomial model with a log link. We recorded 49 bird species belonging to 28 families and 9 orders. The mean diameter of trees had a positive influence on bird abundance (β = 0.21, z = 3.25, p = 0.001), while shrub cover had a negative influence (β1 = − 0.17, z = − 2.18, p = 0.029). When the same model was applied, considering the diameter and height of the largest tree, canopy coverage, and shrub cover emerged as variables with a significant negative association with bird abundance. The findings of this study have implications for the configuration of vegetation structure to maintain avifaunal diversity and enhance the recreational functionality of sacred groves.