Impacts of Water Level on Multidimensional Waterbird Diversity in a Wetland of Yangtze River Floodplain: Insights for Conservation

Anthropogenic hydrological modifications have profoundly altered natural hydrological regimes, which are widely acknowledged as a key driver of waterbird diversity in wetland systems. However, the pathways linking water level to multidimensional waterbird diversity and seasonal variation remain poorly understood, limiting targeted conservation and sustainable wetland management. To address these, based on an annual survey data from Shijiu lake in the Yangtze River Floodplain, we examined the direct and indirect effects of water level on the taxonomic, functional, phylogenetic diversity of waterbirds across annual, wintering, and non-wintering periods. Piecewise structural equation models showed that water level influenced multidimensional waterbird diversity primarily through indirect pathways mediated by local habitat conditions, including water area (WA) and vegetation condition (NDVI). The strength of these indirect pathways differed between the wintering and non-wintering periods. Moreover, generalized additive models revealed seasonally distinct response patterns of multidimensional waterbird diversity to these habitat variables, consistent with the seasonally mediated effects of water level. Overall, our results reveal seasonal differences in waterbird community responses to water level changes. These findings underscore the need for targeted, seasonally responsive hydrological management following future dam construction in lakes and provide practical guidance for waterbird conservation in Shijiu Lake and similar wetland ecosystems.