Drivers of avian community structure and species coexistence in Hong Kong urban parks

Abstract

Mechanisms leading to species coexistence have been a major focus of research in community ecology. One important theory in community ecology suggests that species may segregate from one another in a heterogeneous environment and prevent competitive exclusion, thus allowing species coexistence within a habitat. The concept of heterogeneity applies to both space and time, such that species can segregate spatially and temporally depending on the environment. Although previous studies have investigated the importance of heterogeneity in driving species community structures in natural ecosystems, little research has been conducted in urban ecosystems despite the rapid growth of urban areas globally.

This study evaluates the role of spatial and temporal heterogeneity in shaping urban animal communities using the urban bird community of Hong Kong. Aside from gaining new insights into whether heterogeneity operates similarly in natural versus urban ecosystems, this project will also support urban conservation by providing scientific insights for future urban planning with respect to bird biodiversity, particularly in dense Asian cities.

Throughout the study, 16 urban parks in Hong Kong were surveyed for 10 months, with a total record of 89 bird species and 15,765 individuals. Habitat heterogeneity was not found to be a significant variable driving species richness in urban parks. Percentage ground cover of shrubs was found to be negatively associated with richness of intermediately rare species. However, shrub coverage also positively associated with the abundance of certain species groups, suggesting that processes driving species richness and abundance do not necessarily work in parallel. The morning community in the parks tended to be higher in species richness as well as bird abundance compared to the late afternoon bird community. Temporal segregation within the diurnal cycle was observed between omnivores and non-omnivores, as well as native and exotic species.

Signals of decline of certain bird species in urban parks were apparent when the results here were compared to previous research. However, a high level of biodiversity was still observed. In order to conserve avian species in urban green spaces, it is recommended that urban park designs consider the composition of shrubs to attract more species. Furthermore, the results suggest that habitat heterogeneity may not have a strong influence on species coexistence at fine spatial scales within urban ecosystems but that temporal segregation may be important.