杭州湾及钱塘江河口冬季水鸟群落多样性及其空间分布

在2007、2009和2011年的冬季，对杭州湾及钱塘江河口段曹娥江口至甬江口之间潮间带及其附近围垦区大水面的水鸟群落进行了调查，共记录7目14科69种，其中冬候鸟45种，占总数的65.2％；国家一二级重点保护鸟类7种；超过其东亚地理种群数1%标准的水鸟有6种。研究显示：杭州湾及钱塘江河口湿地越冬水鸟分布的重点区域有4个，即杭州湾慈溪段(记录的水鸟达65种，占总数的94.2%)、钱塘江上虞段（38种，占总数的55.1%）、杭州湾镇海段（37种，占总数的53.6%）和钱塘江海宁段（28种，占总数的40.6%）。对主要类群在4个重点区域的分布比较表明，除与杭州湾镇海段的鸻鹬类分布物种数、钱塘江上虞段的雁鸭类个体数量之间无显著差异外，杭州湾慈溪段分布的鸻鹬类、雁鸭类和鸥类物种最为丰富，该区域记录的鸻鹬类、雁鸭类个体数量也显著高于其它区域。从水鸟群落组成年际动态看， 2007～2011年，杭州湾及钱塘江河口冬季水鸟群落多样性指数变动不大，但个体数量出现了较大波动，雁鸭类和秧鸡类数量呈现增加趋势，而鸻鹬类和鸥类则出现下降态势，且秧鸡类、鸻鹬类及鸥类的个体数量变动最大。湿地资源尤其是滩涂面积可能是影响杭州湾区域水鸟分布的重要因素。拥有大水面的海涂水库、围垦区自然抛荒而待开发的滩涂能为水鸟提供重要的越冬场所。从整个杭州湾来看，人为活动如近年来高强度的大规模围垦可能是导致该区域越冬水鸟群落组成和种群数量发生剧烈变动的主要原因。在加强自然潮间带资源保护的同时，改进围垦区人工湿地的管理，将有利于提高当地乃至整个区域的水鸟多样性水平

COMMUNITY COMPOSITION AND SPATIAL DISTRIBUTION OF WINTERING WATERBIRDS IN THE HANGZHOU BAY AND THE QIANTANGJIANG RIVER ESTUARY

Composition of waterbirds community was surveyed in the Qiantangjiang River Estuary and the Hangzhou Bay in the winters of 2007,2009 and 2011.A total of 69 species were recorded and they belonged to 7 orders and 14 families.Among these bird species,45 species (652 percent of total) were migrants,7 species were national first grade protected wildlife.For 6 species,maximum counts exceeded the 1% of the biogeographical flyway population.The waterbirds were divided into five dominant groups:shorebirds (Charadriiforms),waterfowls (Anseriformes),the Rallidae and gulls (Laridae,Sternidae).And the dominant species were Dunlin (Calidris alpina) in shorebirds group,Falcated Duck (Anas falcata),Spot billed Duck (Anas poecilorhyncha),Common Teal (Anas crecca),Eurasian Wigeon (Anas penelope) in waterfowls group,Common Coot (Fulica atra) in the Rallidae group and Vega Gull (Larus vegae),Yellow legged Gull (Larus cachinnans) in gulls group.And 65,38,37 and 28 species were recorded in Cixi County,Shangyu County,Zhenhai County and Haining County,and accounted for 942%,551%,536% and 406% of total,respectively.The community compositions from four above mentioned key areas were analyzed by using species numbers or individual number of five dominant groups.The species richness of shorebirds,ducks and gulls in Cixi County was remarkably higher than that in the other areas,while there was no significant difference in the number of shorebirds species between the former and Zhenhai County.In Cixi County,the population of shorebirds and ducks were also larger than that in the other areas except that there was no significant difference in the population of ducks between the former and Shangyu County.From 2007,2009 to 2011,there were little changes in the community diversities of wintering waterbirds,but great change occured in the population size of waterbird community and this was mainly due to the changes of the population sizes of shorebirds,the Rallidae and gulls.Over four years (2007-2011),waterbird numbers increased,from the maximum count of 41 712(2007) to 54 393 (2011).The individual number of the Rallidae increased quickly,from the maximum count of 58 (2007) to 17 171 (2011),but that of the gulls declined quickly,from 4 947 (2007) to 1 845 (2011).The results showed that wetland resource availability was the key factor that affected the spatial distribution of waterbirds in the Hangzhou Bay and the Qiantangjiang River Estuary.Recently,the intensive reclamation in the studied area maybe play a key role in influencing the community composition and structure of wintering waterbirds.Artificial wetlands after tidal reclamation can provide important wintering habitats for waterbirds,such as tideland reservoirs were particularly important for waterfowls and shorebirds,new reclaimed but not yet developed areas for waterfowls and the Rallidae.The surface area of the two above mentioned habitat types of artificial wetlands has increased over the study period,and waterbird species such as Common Coot concentrated in these artificial wetlands have tended to increase.Garbage resources are generally of importance in several large gull species such as the Yellow legged Gull’s diet.The reduction of the amount of garbage from the upper reaches of the Qiantangjiang River may be the reason that has resulted in a sharp decrease of the individual number of gulls from 2007 to 2011.Therefore,for the purpose of bird conservation,the local governments should take actions to protect and use natural wetlands reasonably and efficiently.On the same time,appropriate management is needed to improve the quality of artificial habitats