Responses of breeding waterbird communities to environmental changes in subsidence wetlands in the North China Plain

In the context of global degradation and loss of natural wetlands, waterbirds have been increasingly using artificial wetlands as alternative habitats. However, waterbirds are facing various threats in these artificial wetlands, due to dramatic environmental changes induced by anthropogenic activities. Exploring the effects of these changes on the temporal dynamics of the waterbird communities can help understand how waterbirds adapt to environmental changes and thus formulate effective management and conservation plans. In this study, we carried out field surveys on waterbirds and environmental factors across 20 subsidence wetlands created by underground coal mining in the Huainan coal mining area in the breeding seasons of 2016 and 2021. We predicted that the waterbird assemblages (i.e., number of individuals, species richness, Shannon–Wiener diversity, Pielou evenness and species composition) differed between the two years, and that these differences were correlated with the temporal changes in environmental factors. Across the surveyed wetlands, we recorded 26 waterbird species in 2016 and 23 in 2021. For individual wetlands, the number of waterbird individuals and species richness increased by 71.6% and 20.1%, respectively, over the five years, with no changes in Shannon–Wiener diversity and Pielou evenness. The overall increase in the number of bird individuals was mainly caused by an increase in vegetation gleaners and gulls that adapt well to anthropogenic activities. The species composition was significantly different between the two years, which was mainly caused by changes in the number of individuals of dominant species under influence of changes in human activities. For most wetlands, the temporal pairwise β-diversities could be explained by species turnover rather than nestedness, probably due to high mobility of waterbird species and dramatic changes in local environments. Our study suggests that waterbird communities could respond to environmental changes in subsidence wetlands, providing important implications for waterbird conservation in human-dominated artificial wetlands.