Does wetland degradation impact bird diversity differently across seasons? A case study of Zoige Alpine Wetland ecosystem

Wetland degradation is an escalating global challenge with profound impacts on animal diversity, particularly during successional processes. Birds, as highly mobile and environmentally sensitive organisms, serve as effective indicators of ecological change. While previous studies have primarily focused on local community structures and species diversity during a specific season, there is a need to extend the research timeframe and explore broader spatial variations. Additionally, expanding from simple species diversity indices to more multidimensional diversity indices would provide a more comprehensive understanding of wetland health and resilience. To address these gaps, we investigated the effects of wetland degradation on bird diversity across taxonomic, phylogenetic, and functional dimensions in the Zoige Wetland, a plateau meadow wetland biodiversity hotspot. Surveys were conducted during both breeding (summer) and overwintering (winter) seasons across 20 transects in 5 sampling areas, representing 4 degradation levels (pristine, low, medium, and high). Our study recorded a total of 106 bird species from 32 families and 14 orders, revealing distinct seasonal patterns in bird community composition and diversity. Biodiversity indices were significantly higher in pristine and low-degraded wetlands, particularly benefiting waterfowl (Anseriformes, Ciconiiformes) and wading birds (Charadriiformes) in winter, when these areas provided superior food resources and habitat conditions. In contrast, medium and highly degraded wetlands supported increased numbers of terrestrial birds (Passeriformes) and raptors (Accipitriformes, Falconiformes). Seasonal differences in taxonomic, phylogenetic, and functional diversity indices highlighted the contrasting ecological roles of wetlands during breeding and overwintering periods. Furthermore, indicator species analysis revealed key species associated with specific degradation levels and seasons, providing valuable insights into wetland health. This study underscores the importance of spatiotemporal dynamics in understanding avian responses to wetland degradation. By linking seasonal patterns of bird diversity to habitat conditions, our findings contribute to conservation efforts and provide a framework for assessing wetland degradation and its ecological impacts.