Diversity Of Swimming Birds And Ecological Habits Of Some Species In Poyang Lake During Wintering Period

1.The diversity of swimming birds in Poyang LakeThe diversity of swimming birds were studied in the Poyang Baishazhou Nature Reserve and three reclamation areas of Poyang Lake(Wuxing reclamation site,Henghu reclamation site and Kangshan reclamation site)from October 2018 to January 2019,from October 2019 to January 2020 and from October 2020 to January2021.The results were as follows:A total of 77757 individuals of birds belonging to 24 species of 4 families of 4orders were recorded in four areas of Poyang Lake.Among them,the Tundra Swan Cygnus columbianus and Greater White-fronted Goose Anser albifrons were listed in the second national key protected birds.Swimming birds species(21 species)in the Poyang Baishazhou Nature Reserve were significantly higher than those in three reclamation areas(15 species),indicating that the reserve played a very important role in maintaining the diversity of swimming birds.Geese and ducks were stead dominant species in Poyang Lake.In addition to geese and ducks,the dominant species in the three reclamation areas were Great Crested Grebe Podiceps cristatus and Whiskered Tern Chlidonias hybrida,indicating that the artificial habitat is an important supplement to natural habitats,which can provide temporary habitats and foraging sites for swimming birds.2.The ecological habits of swimming birds in Poyang LakeThe ecological habits of swimming birds were studied in the Wuxing reclamation area,the Changhu Lake and Zhushi Lake of Poyang Lake National Nature Reserve from October 2019 to January 2020 and from October 2020 to January 2021.The results were as follows:(1)Time budget:The main behaviors of 11 species of swimming birds were foraging and resting,and the time proportion of foraging behaviors was above 30%.This behavior pattern is a common behavior pattern in the wintering period of swimming birds,which is closely related to energy accumulation.Daily average temperature had a certain influence on the time budget of swimming birds,and swimming birds would cope with winter by increasing foraging or resting time.In different habitats,birds would choose different strategies.For example,Swan Goose Anser cygnoid foraged mainly on grassland(64.49%),and Common Teal Anas crecca rested mainly in shallow water area(44.53%),which was mainly related to the distribution of food.Sex had no significant effect on the time budget of swimming birds,because during the wintering period,the main purpose of swimming birds was to store energy,and there was no need for mating and reproduction.(2)Behavioral rhythm:The foraging peak of Swan Geese,Bean Geese Anser fabalis and Common Teal appeared in the morning(8:00—9:59)and evening(16:00—16:59).The monring peak of foraging behavior of Grey Geese Anser anser and Eastern Spot-billed Duck Anas zonorhyncha(10:00—10:59)appeared later,and the evening peak appeared earlier(14:00—14:59,15:00—15:59),indicating that the birds foraging in the same area would choose the different time to foraged and reduce competition.The six kinds of birds all had a peak rest at noon,because the temperature was high at noon,and birds did not need to increase extra exercise to maintain body temperature,but reduced energy consumption by rest.Move peaks invariably occurred in the morning,noon and evening,which is related to the alternation of foraging and resting.Poultry repair behavior always occurred before and after rest,so the peak of grooming behavior always occurred before and after the peak of resting.(3)Foraging behavior:The foraging patterns of 11 species of birds were similar,and they were mainly dipping with head-neck submersed(43.41%—80.77%).However,there were large differences in body shape among different birds,and there were large differences in foraging water depth,resulting in niche differentiation of feeding space and reducing competition caused by niche overlap of food factors.The feeding frequency of large-sized swimming birds such as Swan Geese,Bean Geese,Greater White-forehead Geese and Grey Geese was lower than 10t·min^-1,while the foraging frequency of small and medium-sized swimming birds such as Common Teal,Eurasian Wigeon Mareca penelope and Ruddy Shelduck Tadorna ferruginea was higher than 15t·min^-1,indicating that the foraging frequency may be related to the body shape of swimming birds.The foraging frequency of Tundra Swan in the morning(8:00—10:59)was significantly lower than that in the noon(11:00—13:59)and afternoon(14:00—16:59),probably due to lower temperatures in the morning.The foraging frequency of Common Teal in the morning was significantly higher than that at noon and afternoon,which might be due to the increased foraging frequency of Common Teals to compensate for the energy consumed at night.There were certain differences in the duration of single foraging among different swimming birds.The duration of single foraging of Tundra Swan,Swan Geese,Grey Geese,Eastern Spot-billed Duck,Eurasian Wigeon and Mallard Anas platyrhynchos increases with the depth of foraging water,indicating that the shape of swimming birds determines the duration of foraging to a certain extent.3.The the distribution of swimming birds in Poyang LakeThe the distribution of swimming birds in different habitats were studied in tthree reclamation areas of Poyang Lake,and the stable habitats of Tundra Swan,Swan Geese,Bean Geese and Greater White-fronted Goose were studied from October 2018 to January 2019,from October 2019 to January 2020 and from October2020 to January 2021.The results were as follows:(1)Habitat utilization and niche divergence of swimming birds:shallow water area(41.74%)and grassland(37.85%)were the two habitats with the largest number of swimmers,and their similarity was the highest(0.433),which was consistent with the ecological habits of swimmers.The niche overlap of Tundra Swan and Swan Geese,Bean Geese and Greater White-fronted Goose were high(0.911,0.844),because the ecological habits of four kinds of swimming birds were similar,the resource competition was fierce,and it was difficult to form large differentiation.The species pairs with low overlap,such as Tundra Swan and Eastern Spot-billed Duck(0.390),Tundra Swan and Common Teal(0.388),realized the differentiation of spatial niche due to the large body size difference,so as to realize coexistence.(2)Habitat selection:At 500m,1000m and 3000m scales,the main habitat types of Tundra Swan,Swan Geese,Bean Geese and Greater White-fronted Goose were water,accounting for 74.35%—99.21%.The four kinds of birds are phytophagous animals,mainly forage on the rhizome of plants,and a large number of aquatic plants in water habitats can ensure their food sources.Four kinds of birds have a certain proportion of farmland habitats at different landscape scales,so these birds can move to artificial habitats(farmland)to forage rice when food was scarce in waters.At the micro-habitat scale,the substrate types of migratory birds habitat were divided into water,vegetation and mud.The factors affecting the selection of micro-habitat habitat are safety(distance from interference source and concealment),water factor and food factor.In the protection of swimming birds habitats,on the one hand,it is necessary to reduce the human disturbance factors around the habitats,on the other hand,it is necessary to maintain the habitats with a certain water area and vegetation coverage,in order to ensure the safety of the bird habitat environment and sufficient food resources.In addition,farmland around the Poyang Lake area is sometimes a temporary feeding place for a large number of migratory birds such as Tundra Swan,Swan Geese,Bean Geese and Greater White-fronted Goose.It is recommended to retain part of the grain during harvest in paddy fields where a large number of yaniformes have been seized to provide supplementary food resources for these large-sized swimming birds.