Waterbird Community Diversity And Spatio-temporal Dynamics In Sihong Hongze Lake Wetland National Nature Reserve

Hongze Lake is the fourth largest freshwater lake in China and an important stopover and wintering site for waterbirds,but there is a relative lack of research on waterbirds in Hongze Lake Wetland.In this study,a monthly field survey of waterbird communities in Sihong Hongze Lake Wetland National Nature Reserve(hereinafter referred to as "Hongze Lake Reserve")was conducted from July 2020 to June 2021,2023,using the sample line method and sample point method.The waterbird community diverstiy,spatial-temporal dynamics and feeding guild were analyzed,and the interspecific correlations between the two main groups of plovers and geese and ducks,as well as differences in wintering behavior and temporal distribution of the dominant geese and ducks,were explored.The main findings are as follows:1.A total of 132,638 waterbirds were recorded from July 2020 to June 2021,belong to 82 species in 7 orders and 14 families.Of these,a total of 75 species were recorded in this survey,seven species were recorded based on historical documentation and birdwatching records from protected areas.Water birds of Charadriiformes were the most abundant in species number,followed by Anseriformes.2.The seasonal dynamics of waterbirds in the Hongze Lake Reserve were evident.In terms of number of species,more waterbird species were recorded during the spring and autumn migration seasons,with 52 and 56 species,respectively,and 38 and 30 species distributed in winter and summer,respectively;in terms of numbers,the highest number of birds were recorded in winter,followed by autumn,spring and summer,respectively.The number of waterbird species,population size and species diversity indices varied within months: peak species numbers occurred in March and November;peak numbers occurred in December and January;peaks in the Shannon diversity index for waterbird communities occurred in April and September during the waterbird migration period,and the Pielou homogeneity index for waterbirds remained high from April to July.Bird community similarity was higher between June and July,and between December and January,and lower between September and November,and September and December.Interspecific correlations between the 12 species of shorebirds and ducks showed that seven pairs of shorebirds and 46 pairs of ducks were significantly or very significantly positively correlated.3.The number of species,population size and diversity index of waterbirds in Hongze Lake Reserve varied within habitats.In terms of number of species,the highest number of waterbird species was recorded in the shoal(65),followed by open water(31),phragmite saustralis wetland(30)and aquaculture pond(22);in terms of number,the highest number of waterbirds was recorded in open water,followed by shoal,phragmite saustralis wetland and aquaculture pond respectively;The Shannon Diversity Index(H’=2.42)was highest for waterbird communities in phragmite saustralis wetland,followed by aquaculture pond(H’=2.19),shoal(H’=2.09)and open water(H’=1.42),respectively.The Beta diversity distribution pattern showed that the Beta diversity turnover component was higher than the nested component between open water,phragmite saustralis wetland and aquaculture pond,while the nested component was higher than the turnover component between the rest of the habitats.4.The study of waterbird feeding groups in the Hongze Lake Reserve showed that waterbirds in the reserve can be divided into four feeding groups,deep-water feeding group(G1),digging and pecking group(G2),shallow-water feeding group(G3)and mudflat scouting group(G4).The G2 digging and pecking group had the highest number of waterbird species(29),mainly in the duck family,while the G1 deep-water feeding group had the highest number of waterbirds,mainly in the ruffe family.Waterbird feeding groups differed between seasons and habitats: the most abundant waterbird feeding group species were recorded in autumn,while the largest number of waterbird feeding group species were recorded in winter;the most abundant waterbird feeding group species were recorded in shallow habitats,while the largest number of waterbird feeding group species were recorded in open water.Results of the composition of waterbird feeding groups in the different seasons and habitats of the reserve showed that the species composition of waterbird groups was relatively most similar between spring and autumn,and between reed swamps and shallows.5.A study of the behavioral patterns of the four dominant species of geese and ducks during the wintering period in the Hongze Lake Reserve showed that movement(45.65%)accounted for the largest proportion of behavior,followed by resting(26.34%),foraging(23.16%)and other(4.85%)behavior.The results of the time allocation of the four species of geese and ducks in different habitats showed that the time allocation of foraging behavior was high in shallow water habitats with abundant aquatic vegetation and low water levels(21.87%±1.05% for the Sibirionetta formosa;37.75%±1.46% for Anas crecca;24.40%±0.86% for the Anas platyrhynchos;and 42.66%±1.29% for Anas zonorhyncha);in deeper water,where the lake is open with weak human activity,the time allocation for resting behavior is higher for Sibirionetta formosa,Anas platyrhynchos and Anas zonorhyncha(23.25%±0.92%;42.69%±1.20%;38.43%±1.18%);in addition,other behaviours such as vigilance were higher for Anas crecca,Anas platyrhynchos and Anas zonorhyncha in shallow water closer to the river bank and with more anthropogenic disturbance than in deeper water away from the river bank due to human activity.In summary,the waterbird communities in the Hongze Lake Reserve are rich in diversity,and the composition and structure of the waterbird communities have obvious seasonal characteristics,and the diverse habitats in the reserve are important for maintaining waterbird diversity.To address the problem that the high water levels in winter and spring and the low water levels in summer,which are the opposite phases of the reserve due to the South-North Water Diversion Project,limit the number of plover snipe in the area,which suggested that the reserve can adopt management methods such as artificially regulating water levels and modifying shoreline habitat patterns,and hence providing more available microhabitats for waterbirds.