Abstract:

Aims: Small wetlands are an important part of urban ecosystems and important shelters for wildlife. Bird diversity as an indicator of urban small wetland ecosystems, its spatial and temporal patterns are affected by many environmental factors. In this study, we studied urban small wetlands and their birds to identify the key environmental factors that affect the spatial and temporal patterns of bird diversity in small wetlands. We then make suggestions on the construction and management of urban small wetlands to promote the protection of urban birds and their habitat restoration.
Methods: A total of 45 small wetlands in Hefei City were taken as research units, and we used the fixed radius method to investigate the distribution of bird species and their abundance from August 2020 to July 2021. A number of environmental factors were also measured, including wetland area, wetland shape, proportion of construction area, proportion of vegetation area, environmental noise, man-made disturbance, and urbanization index. The spatial and temporal characteristics of bird diversity in urban small wetlands were studied by α and β diversity analyses. Then, the model selection and model averaging based on information theory were used to determine the main environmental factors affecting α diversity of bird communities, and the multiple regression model based on distance matrix were used to determine the main environmental factors affecting β diversity of bird communities and their components.
Results: A total of 13 orders, 39 families, and 102 bird species were found in the surveyed wetlands, including 31 waterbird species. There were 2 species in the List of National Second-Class Key Protected Wild Animals, 17 species in the List of Key Protected Wild Animals of Anhui Province, and 1 Vulnerable (VU) species on the IUCN Red List of Species. The results indicated that the α diversity and β diversity of terrestrial birds and waterbirds in small wetlands were both significantly affected by wetland area and urbanization index. The proportion of vegetation area had a strong effect on terrestrial bird diversity, while the proportion of construction area had a significant effect on waterbird diversity. Meanwhile, the species richness of waterbirds and terrestrial birds were both positively correlated with wetland area. The species richness of waterbirds was negatively correlated with the urbanization index, while the species richness of terrestrial birds increased initially and then decreased as urbanization increased. The species richness of terrestrial birds peaked at the small wetlands between intermediate urbanization intensities and low urbanization intensities. When the area of the wetland was about 4 ha, the wetlands could maintain more waterbird species. In addition, terrestrial bird species richness was positively correlated with the proportion of vegetation area, while waterbird species richness was negatively correlated with the proportion of construction area. Beta diversity and species nestedness increased with the increase of key environmental factors, while species turnover exhibited an opposite trend. Furthermore, the results of total β diversity and its compositions indicated that the turnover component of species was predominant, signifying that small wetlands have important conservation significance as a meta-ecosystem.
Conclusion: Our study indicates that wetland area, urbanization index, the proportion of construction area, and the proportion of vegetation area were the key environmental factors affecting bird diversity in small wetlands. On the premise of protecting all small wetlands, we suggest that small wetlands with large areas should be retained and constructed. We must pay more attention to protect small wetlands with intermediate and low urbanization intensities. In addition, the area of natural vegetation should be retained and increased during the management and construction of small wetlands, and the number of artificial structures should be reduced.

Key words: beta diversity, alpha diversity, small wetland, bird communities, environmental factors, Hefei City