Intra-annual Compositions and Diversity Variations of Waterbird Communities in China

Waterbirds are often used as indicators of wetland biodiversity and ecosystem health due to their sensitivity to environmental changes. However, most studies have focused on long-term variations of waterbird communities, while the intra-annual changes have rarely been investigated. Here, we analyzed the seasonal dynamics of compositions and the intra-annual variations of species richness and abundance of waterbird communities among the nine major river basins of China, and focused on the effects of different residential types and taxonomic groups on the diversity variations. In most of the nine basins, the waterbird communities in spring and autumn showed high similarity, while those in summer and winter were quite different. Such a seasonal cycle of species composition was caused by the seasonal migration of waterbirds. The season with higher species richness shifted from summer to winter as the latitude of the basin decreased within China, but almost all basins had the lowest community abundance in summer. This was because the variation of richness was directly influenced by the variation in species composition, but the variation of abundance was more influenced by the population size of different waterbird assemblages. Our results emphasized the importance of seasonal dynamics of waterbird communities to the understanding of their migration patterns, and highlighted the impact of different waterbird assemblages on intra-annual community variations. Additionally, we also noted the potential effects of population size and behaviors at different parts of the waterbird life circle on the observations of them. The information gathered in this study will provide guidance for the conservation of waterbird species and their habitats.