Abstract:

Aims: To determine the nestedness distribution patterns and their influencing factors for communities of all birds, forest birds, and waterbirds in Zhengzhou urban parks.
Methods: Bird data were collected for 15 urban parks in Zhengzhou City, Henan Province, from March to July of each year from 2019 to 2022 at the China Bird-watching Record Center (http://www.birdreport.cn/). The data were further checked and corrected according to A Field Guide to the Birds of China and A Checklist on the Classification and Distribution of the Birds of China. For each urban park, we collected five habitat variables (park area, two isolation indices, number of habitat types, and building index), which are generally thought to influence nestedness patterns. For each species, we selected four life-history traits that reflect extinction and migration tendencies: body size, geographic range size, clutch size, and minimum area requirement. We used WNODF (weighted nestedness metric based on overlap and decreasing fill) to calculate the nestedness patterns of bird communities. We used the ss null model algorithm to randomly generate 1,000 matrices and estimated statistical results within a 95% confidence interval.
Results: From 2019 to 2022, 234 bird species belonging to 53 families and 17 orders were recorded in the 15 urban parks, including 144 forest bird species belonging to 33 families and 4 orders, and 67 waterbird species belonging to 13 families and 7 orders. Among the 234 bird species, 5 species were endemic to China, 2 species were classified as first-class national protected animals, and 30 species were classified as second-class national protected animals. The number of bird species surveyed in each park ranged from 19 to 135. The WNODF analysis results showed the avian communities in Zhengzhou urban parks were significantly nested. The nestedness communities of all birds, forest birds, and waterbirds in Zhengzhou urban parks was significantly associated with park area and certain extinction-related ecological characteristic (minimum area requirement). The habitat-site matrix in Zhengzhou urban parks was also significantly nested, which agrees with the habitat nestedness hypothesis. The building index, a measure of urbanization degree, also affected the the nestedness of waterbird assemblages. However, the nestedness of communities of all birds, forest birds, and waterbirds in Zhengzhou urban parks was not correlated with two isolation indices and body length, rejecting the selective immigration hypothesis. The nestedness of communities of all birds, forest birds, and waterbirds in Zhengzhou urban parks also did not support the passive sampling hypothesis.
Conclusions: The nestedness patterns for communities of all birds, forest birds, and waterbirds in Zhengzhou urban parks are consistent with the selective extinction hypothesis and habitat nestedness hypothesis. To effectively conserve bird diversity, large parks with diverse habitats should be protected because park area and habitat diversity are important factors affecting the nestedness patterns of bird assemblages. In addition, bird species with large minimum area requirements should be given prior protection since these species are at a higher risk of local extinction. Finally, as waterfowl and forest birds respond differently to urbanization, these two types of birds should be treated differently when considering conservation strategies.

Key words: birds, nestedness, selective extinction, urban park, habitat nestedness, WNODF