Short communication Changes in Tundra Swan Cygnus columbianus bewickii distribution and abundance in the Yangtze River floodplain

PEIHAO CONG, LEI CAO, ANTHONY D. FOX, MARK BARTER, EILEEN C.REES, YONG JIANG, WEITOU JI, WENZHONG ZHU and GUOXIAN SONGApproximately 75% of the East Asian Flyway Tundra Swan Cygnus columbianus bewickiipopulation winters in the Yangtze River floodplain, China. Historically the species was morewidely distributed throughout the floodplain but now most of the population is confined to fivewetlands in Anhui Province and to Poyang Lake in Jiangxi Province, where the majority (up to113,000 birds) occur. Within-winter counts suggest that swans congregate at Poyang Lake beforedispersing to other sites later in the winter. Counts show large between-year fluctuations,but suggestdeclines at Shengjin and Fengsha La kes (both in Anhui) during the last five years. Declines atShengjin Lake are likely due to decreases in subme rged vegetation (particularly tuber-producingVallisneria, a major food item) perhaps linked to eutrophication. Range contractions throughout thefloodplain may also be linked to reductions in submerged vegetation coverage elsewhere. Changes inwater quality and lake hydrology post-Three Gorges Dam may have adversely affected submergedvegetation productivity. Key information needs for the effective implementation of conservationmeasures for Tundra Swans include: ( 1) annual surveys of all major wintering sites throughout eachwinter to establish the importance of different sites during the non-breeding period; ( 2)moreinformation on swan diets at important sites; and ( 3) an assessment of adverse effects of water qualityand lake water levels post-Three Gorges Dam on submerged vegetation productivity at Poyang Lakeand other important sites.