Study On The Community Structure Of Waterbirds Wintering At The Lakes In Yangtze River Floodplain In Anhui Province

The shallow lakes in the middle and lower Yangtze River floodplain in Anhui province are important habitats and stopover sites for wintering waterbirds on the East Asian—Australia Flyway. In recent years, with the increasing of fishery in the lakes, the wetlands of the lakes deteriorate seriously, as it takes adverse effect on ecosystem structure and function, threatened waterbirds wintering in lakes. The seasonal dynamics, relationships between habitat factors, resource utilization of guilds of wintering waterbird communities were surveyed in the lakes in order to provide basic data for protecting of waterbird resouces. The main results were as follows.1. A total of 56 species and 155560 individual of waterbirds were counted during the surveys, Geese (Anser cygnoides), Bean geese(Anser fabalis). Tundra Swan (Cygnus columbianus) and Dunlin (Calidris alpina) were the dominant species in those shallow lakes. The species number and individual assemblage reached the maximum by the end of December and early January every year, but the largest flocks for different ecological groups occurred not in the same time. The spatial distribution of waterbirds was related to the fishery patterns. The habitats of waterbirds can be divided into three groups, the crab pond, crab and fish pond, and nature area group. ANOVA method was used to analyze the density of dominant waterbirds at the three different zones. Results showed that the density of Cranes, Geese and Ducks were very significantly different between farming ponds, and natural area (P<0.01). The different fishing pattern had a significant impact on dominant species of wintering waterbirds, such as Cranes and Anserifomes.2. The characters of resource partitioning of the waterbird assemblages were studied in the shallow lakes. We collected foraging behavior data of 30 species waterbirds by instantaneous scan sampling in Shenjin Lake, Caizi Lake and Wuchang Lake, the three sallow lakes along the Yangtze River in Anhui Province, China, and then divided the wintering waterbird assemblage into guilds by using clustering method. DCA analysis was also used to analyze the resource partitioning characteristics of the waterbirds. The results show that the wintering waterbirds could be divided into four groups, the deep water foragers, shallow water foragers, peckers and diggers, pickers in mudflat. Most species were in the G2 group, such as swan geese, bean geese; and the second was G3 group, with tundra swan, Eurasian Spoonbill; G4 group was composed of dunlin, spotted redshank and common redshank. The foraging substrates of those guilds were mainly in the lake beaches or littoral zones.DCA analysis showed that food resources together with foraging strategies determined the characteristics of the resources partitioning of the wintering waterbird guilds in the sallow lakes. The foraging modes of waterbirds in grassland were mainly stay-feed and peck, and pause-travel was used by the guild foraging in mudflat, while diving was used by the guild in profundal zones. In habitats, foraging strategies composing of foraging behavior and move mode had a significant positive correlation to the foraging guilds, which was the basis of resource partition. First, because the different foraging substrates, making the division of the groups of guilds in shallow water space and food resources, such as deep water forager, shallow water forager and forager on the dry beach. Secondly, within each guild foraging behavior and movement pattern (the discovery of food), making the food resources can be take full advantage of use, for example, foragers on the mudflats and marsh took to pecking and excavation, further subdividing within the guilds feeding space and food resources. So it is important to keep abundant food resources in different lake zones, so as to maintain high waterbird diversity.3. We surveyed the composition of wintering waterbirds community and their habitat characters in three types of wetlands, including mudflat, farmland and aquaculture ponds. During this investigation,40 waterbird species and 53,570 individuals were found in the three types of wetland habitats. The species in the nature mudflat, aquacultural ponds and farmland were 31,27 and 16, respectively. The number was accounted for 51.35%,28.85% and 19.80% in the three types of habitats. This shows different type of wintering waterbirds had their preference on the different habitat. The number of Geese and ducks in three habitats were more than 40%, even more than 80% in auuaculture ponds habitat. Charadriiformes mainly distributed in the natural tidal habitats and aquaculture ponds, paddy fields had less. Crane mainly distributed in tidal habitat and rice fields, while the stork could be found in the three habitats. Using DCA method, habitat factors were ordered on the parameters of waterbirds community by the species and number. The results showed that water area, vegetation height and width of mudflats were positive effect on the species and number of waterbirds, while the human disturbance and total mudflats area had negative effect on them. Average water depth was much closer to the types of parameter species, as indicated that it had a greater effect on waterbird species, and total vegetation cover and submerged vegetation coverage were closer to the number of parameters, indicating that these two factors had effect on waterbird number more than species. With the increase of water level in Caizi Lake and the Yangtze River in late winter, the aquaculture pond and rice fields were major wintering habitats for migratory birds.