Poyang Lake is a key habitat for waterbirds along the East Asian–Australasian Flyway. Understanding the spatiotemporal dynamics of wintering waterbird diversity is critical for optimizing regional wetland conservation. Using waterbird survey data from 44 sites during 2013–2023, we quantified species richness, abundance, Shannon diversity and Pielou evenness to assess interannual trends, feeding-guild responses, contrasts inside versus outside protected areas, and spatial patterns of diversity. We recorded 109 wintering waterbird species from 7 orders and 16 families. Total abundance showed no significant long-term change, but community structure shifted markedly. Feeding guilds responded differently: diversity increased in guilds feeding on sedges and grasses, whereas the abundance of invertebrate-feeding guilds declined and tuber-feeding guilds showed a weak declining trend that was not statistically significant. Diversity was generally higher inside protected areas, yet abundance decreased inside reserves and increased outside, suggesting a redistribution of birds towards surrounding habitats. Based on mean Shannon diversity and its temporal change, sites were classified into diversity core, degradation-warning, recovery-potential and vulnerable areas, revealing strong spatial differentiation in wintering waterbird diversity across the lake. Against a backdrop of overall numerical stability, our results indicate substantial structural and functional reorganization of wintering waterbird communities and support tiered, spatially differentiated management that integrates feeding-guild responses and protected-area versus non-protected patterns to enhance population and habitat resilience in Poyang Lake.