| The abundance of food resources,availability and their spatial distribution are the key factors that greatly affect the foraging strategies of wintering waterbirds,especially the spatial distribution,biomass,growth condition of food resources,which directly affect the foraging activities and habitat use,so it had important theoretical significance for population protection to study the condition of food resources and foraging behavior.In this paper,greater white-fronted goose(Anser albifrons)wintering at Shengjin Lake was taken as the research object,and focal animal sampling and instantaneous scanning sampling method were used for collecting data about behavior and population in meadows,mudflats,paddy fields during September 2017 and April 2018,and the food resource data in the three habitats,including biomass,plant height and water content were also collected every month.Based on these data,non-parametric test was used to analyze the time allocation and habitat selection characteristics of various behaviors of the wintering geese.The correlation between foraging rate and various environmental factors was tested by Pearson correlation analysis,and the ecological factors affecting foraging rate of wintering greater white-fronted goose was analyzed by linear regression model.The main research results are as follows:During the whole wintering period,the food resources of geese showed a trend of unimodal distribution,and there had the most abundant food resources in meadows.In the early overwintering period,there were the most abundant food resources(295.64±46.07 g/m~2,n=30)in meadows,followed by paddy fields(110.17±32.40 g/m~2,n=27),and the lowest was in mudflat habitats(19.23±6.78 g/m~2,n=27).In the middle wintering period,the food density of paddy field decreased significantly(45.22±20.57g/m~2,n=27),while the food resources of meadows increased significantly(595.88±27.08g/m~2,n=27).During the late wintering period,the food resources of the three habitats decreased significantly,but during the whole wintering period,there were significant differences about the food resources between meadows and paddy fields(P=0.05,P=0.018).During the six stages of wintering period,the height and water content of Carex also showed bimodal distribution trend.The average plant height of Carex was 0.14±0.21 m(0.04-0.2 m,n=243),and the highest plant height was 0.17±0.06 m from March 16 to April 6,the next height range was December 16 to January 15 of the next year,which was 0.16±0.04 m.In addition,the two peaks of the water content of Carex during wintering period were 231.47±80.28 g/m~2 on November 16 to December 15and 187.44±33.17 g/m~2 on February 16 to March 15,and it was found that there was the least water content(48.54±21.33 g/m~2)on January 16 to February 15.Moreover,the plant height and water content of Carex showed significant differences throughout the wintering period(P=0.002),and showed a positive correlation.The population of geese in six main habitats of Shengjin Lake showed unimodal distribution on the time axis,and the population number is positively correlated with food resources and temperature.The geese arrived in the Shengjin Lake in September every year,and the population size reached the maximum in late December,then the number gradually declined,and the wintering ended at the end of the next March.In the wintering period,analysis about the correlation among the population number,food resources and temperature in the habitat of Yangetou indicated that the population number and food quantity were significantly positively correlated(P=0.000,R~2=0.579),and positively correlated with the minimum temperature(P=0.001,R~2=0.580).Foraging behavior had the highest proportion in ethogram during the whole wintering period with 41.33%±28.08%in the early stage,29.09%±17.44%in the middle stage and 39.15%±11.01%in the late stage,but there was no significant difference among them.In the process of overwintering at Shengjin Lake,the greater white-fronted goose spent the most time on foraging in the meadow,the abundant Carex resources could provide more energy,mudflat habitats were followed,and paddy fields had the least foraging time.There was no significant difference in the foraging time distribution between the meadows(P=0.11)and the paddy fields(P=0.21)during the whole wintering,but there was a significant difference in the mudflat(P=0.02).Moreover,it was found that there were two optimal foraging periods in the process of foraging Carex,namely 15 days after early November and 30 days after early February of the next year.The food resources were the most important factor affecting the wintering of the greater white-froned goose at Shengjin Lake.Regression analysis was conducted to explain the factors affecting foraging behavior,including food resources,minimum temperature,plant height,habitat area and population size,and so on,it was found that the plant height(R~2=0.570,P=0.012)and food density(R~2=0.417,P=0.044)had a better goodness of fit with foraging rate,and the minimum temperature(R~2=0.126,P=0.314)had no significant relationship with foraging rate.Through AIC criterion,the candidate model was sorted and the optimal factor was selected,and it was obvious that the food resources were the most important factor affecting foraging behavior of wintering geese. |
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