Abstract:

Aims: Urbanization is one of the main causes of the rapid loss of biodiversity. Urban birds are an important part of the urban ecosystem, and their biodiversity patterns as well as species conservation have become the hotspots of urban ecology research. This study aims to reveal the diversity and nestedness of bird communities on the fragmented woodlots in urban and suburb areas, so as to provide data support for the protection of bird diversity in urban ecosystems.
Methods: We surveyed the diversity of birds on 13 urban and suburb woodlots of Haikou and Sanya cities. We used line-transect method and sampled the birds during two breeding seasons (spring and summer) of 2021. We analyzed the nestedness of the bird communities by using the NODF (nestedness metric based on overlap and decreasing fill) and WNODF (weighted nestedness metric based on overlap and decreasing fill). We used linear modelling to examine the relationships between the species richness and patch characteristics (area, the distance to the nearest larger woodlot).
Results: (1) We recorded 100 forest birds in total, which belong to 11 orders and 39 families. The species richness was higher in Sanya suburb, with 68 forest birds belonging to 8 orders and 29 families. We recorded 18 species of the national key protected birds and the number of the protected species in suburb were higher than other in urban regions. We recorded the yellow-breasted bunting (e.g. Emberiza aureola) in Haikou suburb, which is the first-class state protection bird in China. (2) There were significant differences in the abundance, species richness, Pielou evenness index and Shannon-Wiener diversity index of bird assemblages among four regions. The abundance of birds in urban of Haikou was significantly higher than in suburb of Haikou (P < 0.05). The species richness, Pielou evenness index and Shannon-Wiener diversity index of bird assemblages in suburb of Sanya were both significantly higher than in urban of Sanya and suburb of Haikou (P < 0.05). (3) The results of nestedness analysis showed that the bird assemblages were anti-nested among the woodlots in two cities. The bird species richness was only significantly and positively correlated with woodlots area in Sanya. The distance to the nearest larger woodlot had no significant effect on bird species richness in two cities.
Conclusion: Our study showed that the species diversity of bird assemblages overall was higher in the suburb areas than in the urban. The niche of avian communities in urban was dominated by a handful of species (e.g. Pycnonotus sinensis). The high urbanization of the Haikou City might induce the homogenization of bird assemblages between the suburb and urban areas. The anti-nested distributed structure of bird species may be the result of the high mobility, the interspecific competition of the birds, or the availability of food resources in the woodlots. We recommend that the conservation of birds in both urban and suburban areas should strengthened, and the destruction of woodlots should be prohibited to improve the diversity of birds.

Key words: urbanization, suburb, species richness, nestedness