Factors affecting avian species richness and occupancy in a tropical city in southern China: Importance of human disturbance and open green space

A majority of urban avian research has concentrated on urbanization intensity and vegetation characteristics. However, other built-up and non-built-up characteristics that can represent environmental gradients within a city are less considered, especially in subtropical/tropical cities of Asia. During 2015–2016, we examined how intra-urban environmental characteristics influenced avian species richness and occupancy in a city in southern China located in the Indo-Burma biodiversity hotspot. We used a hierarchical multi-species occupancy model with five environmental predictor variables: PC1, increasing human disturbance with building height; PC2, a gradient from low commercial to tall residential building in winter, and decreasing commercial building and noise in summer; PC3, a gradient from residential to commercial building, especially low residential to tall commercial building; OPEN, area of open green space (small vegetable croplands and weedy patches); BU, area of built-up structures (landscape variable). Species richness and occupancy of most species showed consistently negative responses to PC1 in both winter and summer. PC2, PC3 and BU did not influence species richness and occupancy. Although effects of OPEN on species richness were not strong, species-level responses revealed significant patterns. In winter, seven species (six that prefer open habitats) showed strongly positive responses and three species (all preferring trees and shrubs) negative responses to OPEN. In summer, three species (two that prefer open habitats) responded positively to OPEN, with no negative responses. Our results suggest that local-scale human disturbance associated with human activities, noise, and taller building heights, could be a stronger factor affecting avian species than the amount of built-up structure at the landscape scale. Our results further indicate that open green spaces, largely composed of small vegetable farms that are often observed in cities in China, may play a positive role to enhance urban avian diversity.