Sex Ratios and Age Structure of Several Waterfowl Species Wintering at Poyang Lake, China

The sex ratios of four dabbling duck species were investigated by point count method during the wintering period between October and the following April from 2012 to 2014 at 45 survey sites of Poyang Lake. From October 2013 to April 2014, the age structure of the Tundra Swan was surveyed by point co...

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Veröffentlicht in:Pakistan journal of zoology 2016-06, Vol.48 (3), p.839
Hauptverfasser: Shao, Mingqin, Chen, Bin, Cui, Peng, Dai, Nianhua, Chen, Hongyu
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Sprache:eng
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Zusammenfassung:The sex ratios of four dabbling duck species were investigated by point count method during the wintering period between October and the following April from 2012 to 2014 at 45 survey sites of Poyang Lake. From October 2013 to April 2014, the age structure of the Tundra Swan was surveyed by point count method at 45 survey sites of Poyang Lake. In middle wintering stage (from December to February), the sex ratio of common teal Anas crecca (60.66% male, n=361) was male-biased while falcated duck Anas falcata (52.10%, n=286), mallard Anas platyrhynchos (50.00%, n=90) and Eurasian wigeon Anas penelope (49.18%, n=183) were near parity. The male ratio of common teal, falcated duck and Eurasian wigeon all showed a tendency of initially increasing and later decreasing throughout the wintering period while mallard showed a continuous growth trend.The male-biased sex ratios in the common teal may be owing to increased female mortality on both breeding and wintering grounds. The intra-seasonal differences in sex ratios for all the ducks can be partly attributed to earlier arrival of males to wintering areas closer to breeding areas, while females and juveniles head further south. There were greater numbers of females for all the ducks in the early wintering stage (from October to November) and the male ratio increased again in the middle wintering stage, which shows that females arrive at winter areas before males in Poyang Lake. Tundra Swan Cygnus columbianus had relative high juvenile percentage (28.27%, n=3130). In the early wintering and spring migration stages (from March to April), the proportions of juveniles were significantly higher than in the middle wintering stage.This may indicate that family groups with young ones arrived at Poyang Lake to winter before those who did not participate or failed to breed, but returned later to breeding grounds, knowledge about this can provide guidance to management task.
ISSN:0030-9923