Distribution Pattern And Habitat Characteristics Of Winter Waterbirds In The Aquacutural Ponds Of Chongming Dongtan, Shanghai

Shanghai Chongming Dongtan National Nature Reserve is located in the east of the Chongming Island,Shanghai,China,aiming at preserving migrants,winter waterbirds and their habitats.Chongming Dongtan has been greatly impacted since 1950s, because of population increase,demand of land,drainage of the tidal flats, development and so on.The drainage once led terrible damage of the wildlife habitat. For the sake of preserving the wildlife habitat while meeting the need of human being, land near the dam derived from drainage in 1990s was turned into aquacultural ponds instead of farm land.Now the aquacultural ponds support lots of winter waterbirds in winter and some of the migrants in both spring and autumn.The spatial utility pattern of birds reflects their selection of habitats.Based on field survey,data analysis,spatial autocorrelation test,and Ordinary Kriging interpolation,we investigated the distribution pattern of winter waterbirds in the aquacutural ponds of Chongming Dongtan,Shanghai.The results showed that both the community richness and abundance are spatial autocorrelation and clustered distribution;however,ducks had a different pattern from waders:The distribution pattern of ducks turned out to be significantly spatial positive autocorrelation and clustered distribution,while that of waders showed a pattern of non-autocorrelation and random distribution.Ducks had high occurrence in the south of the aquacutural ponds between the 92 dam and the 98 dam.Area with ducks richness from interpolation above 5 was about 426.7 hm~2,which was one fourth of the total research area,and area with ducks abundance from interpolation above 300 was about 279.1 hm~2,one sixth of the total research area.Generally,aquacultural ponds were relatively fit habitat for wintering ducks in Chongming Dongtan.Waders had low occurrence in the whole aquacutural ponds.Waders richness showed somewhat clustered distribution,and the area with waders richness from interpolation above 4 was about 239.4 hm~2,in the south of the ponds between the 92 dam and the 98 dam,which is one sixth of the total research area.While waders abundance turned out to be completely non-correlation,and according to the field survey,more waders were seen in the aquacutural ponds to the east of the 92 dam. Consequently,aquacultural ponds were not so fit habitat for wintering wader as that for ducks.As a supplementary habitat,the aquacultural ponds are playing an important role for the winter waterbirds.There are,however,differences in selecting habitats among groups of winter waterbirds.By classification of the aerial picture taken in April of 2005 for the land cover information,extracting the land cover information of the area with high occurrence of waterbirds,and calculating landscape pattern indices, we tried to investigate landscape characteristics of the artificial wetland habitat related to the different distribution pattern.The landscape indices showed ducks preferred the ponds with well-developed reed vegetation,more reed patches,relatively small proportion of water area and deeper water,while waders favored large proportion of water area and shallower water.The requirement of habitats for different groups of winter waterbirds should be taken into an account when planning land use and managing a natural reserve.Water depth management in winter on the aquacultural ponds may promote the habitat availability,especially for the waders.