The loss and degradation of wetlands worldwide has adversely affected waterbirds, which depend on wetland habitats. Many studies have indicated that effectively managed wetlands can provide alternative or complementary habitats for waterbirds and mitigate the adverse effects of wetland loss and degradation. We review the studies on the habitat variables affecting use of wetlands by waterbirds, and we suggest how wetlands can be managed to provide waterbird habitat. These habitat variables include water depth, water level fluctuation, vegetation, salinity, topography, food type, food accessibility, wetland size, and wetland connectivity. Overall, the practice of wetland management requires integrated knowledge related to the entire wetland ecosystem, and ecosystem-based approach is needed to improve the habitat quality of managed wetlands with considering multiple spatial scales, temporal variability, and trade-off among diverse habitat requirements of different waterbirds. Several priorities for future research and management are also suggested in this paper.

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We studied the changes in wetland habitats and waterbird communities between the 1980s and the 2000s at Chongming Dongtan, a Ramsar site in the Yangtze River estuary, an ecologically important region. This region is an important stopover site for shorebirds along the East Asian-Australasian flyway and is extensively used by waterfowl. A net loss of 11% of the wetland area was estimated during study periods at Chongming Dongtan. The change was dependent on wetland types: while the area of artificial habitats such as paddy fields and aquacultural ponds more than doubled, more than 65% of natural habitats including sea bulrush (Scirpus mariqueter) and common reed (Phragmites australis) marshes were lost over the two decades. An exotic plant species introduced from North America, smooth cordgrass (Spartina alterniflora), occupied 30% of the vegetated intertidal zone by the 2000s. Although waterbird species richness did not change between the 1980s (110) and the 2000s (111), 13 species found in 1980s were replaced by 14 newly recorded species. Moreover, there were more species with declining trends (58) than with increasing trends (19). The population trends of species were affected by residential status and habitat types. Transients, wintering migrants, and habitat specialists were more likely to show declining trends compared to those breeding at Dongtan (including year-round and summer residents) and habitat generalists. Furthermore, species associated mainly with natural wetlands were more likely to decline than those associated mainly with artificial wetlands. These patterns suggest that the loss and change of wetland habitats at Chongming Dongtan adversely affected local population dynamics and might have contributed to the global decline of some waterbird species. Because Chongming Dongtan provides stopover and wintering habitats for many migratory waterbirds, protection and restoration of natural wetlands at Chongming Dongtan are urgently needed.