Habitat Selection And Diversity Change Of Waterbirds Community In Reclaimed Coastal Wetlands In Nanhui Dongtan,Shanghai, China

Reclamation intertidal area is a traditional way to increase the land for agricultural and residential use, port construction and industrial estate. Nanhui Dongtan is one of the key reclamationsite in Yangtze River Delta due to rapid urbanization and economic growth. After reclamation, some of the natural wetlands turned to artificial wetlands, i.e., urban lake wetlands, extensive fish ponds, and abandoned wetlands. Which types of artificial wetlands will be better for waterbirds, and what are the major environmental factors affecting waterbird community composition? We carried out the study to answer these questions.A total of95species corresponding to15families and7Orders were observed during census counts. It is mainly composed of Charadriiformes, Anseriformes and Ciconiiformes, which accounting for52.64%,20%and16.84%of all species, respectively. Transients (42species) and winter (35species) were dominant taxa, accounting for81%of all95waterbird species. However, residents (3species) and summer migrants (15species) were also observed. Coot Fulica atra, Falcated Duck Anas falcate and Gadwall Anas strepera were dominant species, accountingfor24.7%,14.6%and10%of all individuals recorded, respectively.Two species, Black-faced Spoonbill Platalea minor and Falcated Duck Anas falcata, meet the international conservation criterion of>1%of global population size, indicating that the Nanhui Dongtan was an important wintering site for Black-faced Spoonbill and Falcated Duck.Of the95species recorded in the study area, most species were recorded in the extensive fish ponds (77species;81%of the total), followed by the abandoned wetlands (59species;62%), and least species in the urban lake wetlands (40species;42%). Meanwhile, the most species-rich families were Charadriiformes (in the extensive fish ponds and abandoned wetlands) and Anseriformes(in the urban lake wetlands). Waterbird species numbers and densities exhibited significant differences in the six wetlands. Specifically, waterbird species numbers and their densities in the extensive fish ponds (followed by the’abandoned wetland2’) were higher than other wetlands. Meanwhile, Anseriformes and Charadriiformes were dominated in the extensive fish ponds1(the species numbers of these two families) and2(their densities). Ciconiiformes were dominated in the’abandoned wetland2’indicating by the higher species numbers of Ciconiiformes in the ’abandoned wetland2’than other wetlands.Differences in the abundance and richness of waterbirds in six wetlands were simulated with the dominance species accumulation curve in PRIMER5.0version. Results showed that waterbird abundance and richness were higher in the’extensive fish pond1’(followed by the’extensive fish pond2’and the ’abandoned wetland2’) than other wetlands. The urban lake wetlands could attract few waterbird species indicating by the lower abundance and richness of waterbirds in the’urban lake wetland1’than other wetlands. Waterbird abundance and richness were higher in the ’abandoned wetland2’(followed by the extensive fish pond) than other wetlands in autumn, and were higher in the ’extensive fish pond1’(followed by the’extensive fish pond2’) in winter.Impacts of environmental factors on waterbird community composition in three types of wetlands were analyzed with Non-metric Multi-dimensional Scaling (NMDS) ordination. Resulted represented that community compositionand of Anseriformes were positively correlated with deeper water area, anthropogenic disturbance, distance to the seawall, and mean water level, however, Charadriiformes were positively correlated with shallow water area and bare muddy area.More Charadriiformes species were observed in artificial wetlands. However, Charadriiformes density was higher in the’extensive fish pond1’than those in other natural tidal flats, but their densities in the’natural tidal flat2’was higher than that in the’extensive fish pond2’. Charadriiformes density in the’extensive fish pond1’was higher than those in the natural tidal flats in spring, but the density in the’natural tidal flat1’was higher than those in artificial wetlands in autumn. However, the density in the’natural tidal flat2’was higher than that in the’extensive fish pond2’both in spring and autumn. Habitat preference of Charadriiformes showed seasonal difference: their density was higher in the’extensive fish pond1’in spring than that in autumn, however, the density in the ’natural tidal flat1’was higher in autumn than that in spring.Compared to two provious waterbird records, in our study, more Charadriiformes species were observed in the artificial wetlands, however, their densities sharply decreased. Dunlin was the dominant species in all waterbird surveys, including our study. In the provious surveys, Rufous-necked Stint and Great Knot Calidris tenuirostris were dominant species, and Black-winged Stilt was rare species. However, in our study, their population status changed to common, rare and dominant species, respectively.Recommendations are as follows:1) To re-introduce seawater to the abandoned wetlands and control the water level to maintain an adequate area of shallow water and bare mudflats for shorebirds.2) To dynamically control the water depth in the extensive fish pond, so as to provide stable habitats for wintering ducks and diving birds (deep water) in winter and migrant shorebirds (shallow water and bare mudflats) in spring and autumn.3) Convert concrete banks into natural sandy soils with reed marshes in the lake area for the purpose of increasing habitat diversity required for waterbird roosting;and.4) Slow down the speed of the reclaimed land into farmland and industrial land. Land use plans dealing with reclaimed regions convert more land into paddy fields and ponds and replace dry land areas.