Abstract: Urbanization is one of the primary causes of biodiversity loss, presenting a major challenge to human’s efforts to maintain species diversity. However, there are substantial uncertainties regarding how disturbance intensity associated with urbanization affects bird community, particularly in terms of functional composition and diversity. We carried out bird surveys in the urban forests of Longyandong Forest Farm in Guangzhou, a megacity in southern China, and analyzed diversity and trait distribution patterns, aiming to examine shifts in bird community structure and trait-associated ecological strategies under varying disturbance intensities. The results showed that bird species richness and composition did not differ significantly across disturbance levels, and functional richness increased significantly with rising disturbance intensity. Functional dispersion peaked at the intermediate disturbance intensity, showing a unimodal relationship, and was associated with the lowest functional redundancy. At intermediate disturbance levels, functional dominance in terms of body size and weight was significantly higher than that in both low- and high-disturbance forests, showing a unimodal pattern. In contrast, functional dominance related to clutch size decreased significantly with increasing disturbance intensity. Our findings elucidate how the ecological strategies of birds shift along a gradient of disturbance intensity in urban forests, which provides important support for guiding bird conservation and the maintenance of their functional composition during urbanization, particularly in the planning, construction and management of urban green spaces, and the ecological restoration of habitats.

Key words: bird community, functional diversity, disturbance, trait, urbanization