Changes in Tundra Swan Cygnus columbianus bewickiidistribution and abundance in the Yangtze River floodplain

Approximately 75% of the East Asian Flyway Tundra Swan Cygnus columbianus bewickii population winters in the Yangtze River floodplain, China. Historically the species was more widely distributed throughout the floodplain but now most of the population is confined to five wetlands in Anhui Province a...

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Bibliographic Details
Published in:Bird Conservation International
Main Authors: CONG, PEIHAO, CAO, LEI, FOX, ANTHONY D., BARTER, MARK, REES, EILEEN C., JIANG, YONG, JI, WEITOU, ZHU, WENZHONG, SONG, GUOXIAN
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press (CUP) 2011
Subjects:
Cygnus columbianus
Tundra
Tundra Swan
Online Access:http://dx.doi.org/10.1017/s0959270911000098
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0959270911000098
Description
Summary:Approximately 75% of the East Asian Flyway Tundra Swan Cygnus columbianus bewickii population winters in the Yangtze River floodplain, China. Historically the species was more widely distributed throughout the floodplain but now most of the population is confined to five wetlands in Anhui Province and to Poyang Lake in Jiangxi Province, where the majority (up to 113,000 birds) occur. Within-winter counts suggest that swans congregate at Poyang Lake before dispersing to other sites later in the winter. Counts show large between-year fluctuations, but suggest declines at Shengjin and Fengsha Lakes (both in Anhui) during the last five years. Declines at Shengjin Lake are likely due to decreases in submerged vegetation (particularly tuber-producing Vallisneria, a major food item) perhaps linked to eutrophication. Range contractions throughout the floodplain may also be linked to reductions in submerged vegetation coverage elsewhere. Changes in water quality and lake hydrology post-Three Gorges Dam may have adversely affected submerged vegetation productivity. Key information needs for the effective implementation of conservation measures for Tundra Swans include: (1) annual surveys of all major wintering sites throughout each winter to establish the importance of different sites during the non-breeding period; (2) more information on swan diets at important sites; and (3) an assessment of adverse effects of water quality and lake water levels post-Three Gorges Dam on submerged vegetation productivity at Poyang Lake and other important sites.

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