Wetland Restoration Effects on Waterbird Diversity and Habitat Use: A Long-Term Case Study from Chongming Dongtan in Shanghai, China

The continued loss and degradation of wetlands pose major challenges to global waterbird conservation. In response, large-scale wetland restoration projects have been widely implemented worldwide, yet their long-term ecological effectiveness has not been sufficiently evaluated. Here, we assessed the long-term impacts of wetland restoration on waterbird communities at Chongming Dongtan Wetland, China, using 17 years of monitoring data spanning pre-restoration, restoration, and post-restoration phases. Our results suggest that the Ecological Control of Spartina alterniflora and Improvement of Bird Habitats substantially enhanced waterbird diversity, with both species richness and total abundance increasing significantly after restoration. Restored artificial wetlands supported particularly high abundances of waterbirds, confirming their role as critical supplementary habitats alongside natural tidal flats. Notably, different waterbird guilds exhibited pronounced seasonal shifts in habitat use: the Anatidae predominated during the wintering period, whereas Waders dominated during spring and autumn migrations, and the degree of reliance on artificial versus natural wetlands varied markedly between guilds and across seasonal cycles. Beyond local effects, we detected a clear spillover effect, whereby increases in waterbird abundance and species richness were also observed in adjacent non-restored natural intertidal mudflats following restoration. In addition, several threatened and nationally protected species were recorded exclusively during the post-restoration phase, indicating improved habitat suitability for conservation-priority taxa. Overall, our findings highlight that wetland restoration can generate both local and landscape-scale biodiversity benefits, emphasizing the importance of incorporating habitat heterogeneity, seasonal habitat requirements, and spillover effects into coastal wetland restoration and management strategies.