Prelimary Study On Population Ecology Of Wintering Anseriformes In The Wuyuan Section Of Le'an River In The Poyang Lake

The population ecology of wintering Anseriformes was prelimary studied in the Poyang Lake,from wintering period of November 2014 to March 2017.The study content including number & distribution and sex ratios & age structure of Anseriformes,behaviors of Scaly-sided Merganser(Mergus squamatus)and Mandarin Duck(Aix galericulata).Results are as follows:(1)Number & distribution of Anseriformes: A total of 18 species of Anseriformes were recorded.Of these species,tundra swans(Cygnus columbianus)and white-fronted gooses(Anser albifrons)were listed as Class ? national pro-tected species.Bean gooses(Anser fabalis)were the most abundant species,followed by tundra swans,white-fronted goo-ses,swan gooses(Anser cygnoides)and falcate ducks(Anas falcata).Spot-billed ducks(Anas poecilorhyncha)were encountered most frequently,followed by bean gooses,tundra swans,swan gooses and white-fronted gooses.Spot-billedducks,bean gooses and tundra swans emerged in most lakes.Large,shallow lakes,marshland and mudflats were the preferred habitats by most of these wintering waterfowls.Poyang Lake National Nature Reserve supported the most of the birds.(2)Sex ratios & age structure of Anseriformes: In middle wintering stage,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-biased sex ratios in the common teal may be owing to increased female mortality on both breeding and wintering grounds.There were greater numbers of females for all the ducks in the early wintering stage 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 later wintering stages,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.(3)Diving behaviors of Scaly-sided Merganser: Mean dive duration of Scaly-sided Merganser was(18.8± 0.1 s,n =4305)while mean time on the surface was(12.9± 0.2 s,n = 4104),and mean dive efficiency was 2.297±0.025.Mean dive duration and mean time on the surface of males were significantly higher than those of females,which may be related to differences in body mass.With an increase in temperature,dive duration significantly increased.Along with the passage of time of year and daytime,dive duration significantly increased.The difference of diving behavior among various temperatures and time periods may be related to a low minimum rate of oxygen consumption.Dive duration decreased significantly with the increase in flock size,which may be caused by rising intraspecific competition.(4)Energy expenditure of Scaly-sided Merganser: Swimming-energy expenditure of Scaly-sided Merganser was the most(117.96±36.80 KJ/day),followed by feeding-energy expenditure(115.60±38.94 KJ/day)and flying-energy expenditure(104.15±51.34KJ/day),which was consistent with the main physiological needs of Scaly-sided Merganser during nonbreeding season.Male Vigilance-energy expenditure was significantly higher than female(F=4.929,df=1,p=0.033),which was related with the guards work that mainly undertook by male.With an increase in average daily air temperature,the Vigilance-energy expenditure significantly decreased(F=5.816,df=1,p=0.026),which showed that temperature has an important effect on the Scaly-sided Merganser,compelled this specie to adapt different behavior strategy under different environment temperature.With an increase in group size,the Social-energy expenditure significantly increased(F=5.109,df=1,p=0.043),which was caused by the declining time budget of feeding and vigilance which lead to other activity-time budget,such as social time budget accordingly increased.(5)Wintering behaviors of Mandarin Duck: The main wintering behaviors of Mandarin Duck included resting(38.95%),feeding(22.63%),swimming(20.35%)and maintenance(12.80%),which was consistent with other waterfowls,indicating that this combination of behavior could satisfy the basic physiological needs and the balance of energy intake and preservation for wintering waterfowls.