Community Diversity Of Shorebirds And Ecological Habits Of Some Species In Poyang Lake During Non-breeding Period

Poyang Lake is the largest fresh water lake in China,with about six hundred thousand waterbirds wintering in the lake area every year.Among them,shorebirds account for a large proportion of the whole waterbirds in number of species and individuals.The author has done some studies on the community diversity,behavioral time budget and rhythm,foraging strategy and habitat selection and utilization of shorebirds in Poyang Lake during non-breeding period.Our results are as following:1.Community diversityIn January of each year from 2015 to 2022,A survey of shorebirds in the East Poyang Lake National Wetland Park（hereinafter referred to as Poyang）and Nanji Wetland National Nature Reserve（hereinafter referred to as Nanji Wetland）were conducted to study the features of waterbird diversity using the direct count method.A total of 43806 individuals of shorebirds belonging to 17 species of 3 families were recorded in two study areas of Poyang Lake.The Eurasian Curlew（Numenius arquata）is listed in the second category of China’s nationally protected bird species list.It shows that the survey area is rich in shorebirds resources,which plays an important role in the diversity maintenance of waterbirds in Poyang Lake.The Pied Avocet（Recurviostra avoseta）and the Spotted Redshank（Tringa erythropus）were the stead dominant species in the Poyang lake.The number of species for shorebirds in Poyang Lake has no drastic change.Most of the shorebirds in Poyang are concentrated in the two sample areas of Siwang Lake and Dongmen Lake,while most of the shorebirds in Nanji Wetland are concentrated in the three sample areas of Changhu Lake,Sanniwan Lake and Beishen Lake,with a large and stable number.In the two study areas,the number of years and distribution samples recorded by Northern Lapwing（Vanellus vanellus）are the largest.It shows that it has wide distribution range and strong adaptability to habitat.The niche overlap between Northern Lapwing and Spotted Redshank is the highest on both temporal and spatial scales,indicating that the competition between species is more intense.They achieve niche separation by acquiring different food and occupying different micro habitats.From September 2022 to Janunary 2023,A survey of shorebirds in the Wuxing Siberian Crane Conservation Community（hereinafter referred to as Wuxing）and Nanji Wetland were conducted to study the features of waterbird diversity using the direct count method.A total of 20781 individuals of shorebirds belonging to 21 species of 4 families were recorded in the two study areas.Among them,a total of 531 individuals belonging to 10 species of 3 families were recorded in Wuxin.A total of 20250 individuals belonging to 21 species of 4 families were recorded in Nanji Wetland.Extreme drought has led to a large reduction of food resources for shorebird,the lack of suitable habitats and the extreme compression of birds’living space.2.Behavioral time budget and rhythmThe focus animal method was used to study the behavioral time budget and rhythm of Spotted Redshank,Pied Avocet and Black-tailed Godwit（Limosa limosa）in Poyang Lake.The main behaviors of the three shorebirds are foraging and resting.The main behaviors of Spotted Redshank include foraging（71.62%）and resting（20.93%）,and the behavioral pattern was more foraging and less resting.The main behaviors of Pied Avocet include foraging（24.63%）and resting（72.8%）,and the behavioral pattern was more resting and less foraging.The main behaviors of Black-tailed Godwit include foraging（50.67%）and resting（42.31%）,and the behavioral pattern was of equal importance for two behaviors.which is speculated that this difference is related to the difference in body size.These three shorebirds prefer to gather in large groups to forage,so the alerting time of a single individual is relatively small.The foraging behavior of the three shorebirds was significantly negatively correlated with the time allocation of resting behavior（P<0.01）.The proportion of foraging behavior of Spotted Redshank is the highest at all times,and the foraging peak appears in the morning,afternoon and evening,and the resting peak is the opposite in the overwintering period.The foraging peak of the Black-tailed Godwit often occurs after the peak of the Spotted Redshank.Thus these two species formed different foraging peaks and decreased their competition,achieving niche separation.In addition,the foraging peak of the three shorebirds appeared from 15:00 to 17:00 in the afternoon,presumably to cope with the cold night and increase the foraging time to ensure adequate energy intake.3.Foraging strategyThe foraging strategy of shorebirds in Poyang Lake was studied by using the focus animal method.the average foraging frequency and step frequency of the seven shorebirds are more than 20(t·min^-1).The average foraging frequency and step frequency of Ruff（Calidris pugnax）were significantly higher than those of the other six shorebirds（P<0.01）.It was speculated that it was related to its small body size and gathered in small groups for foraging.It is necessary to increase the frequency of foraging and step to obtain enough food.The foraging frequency of the Black-winged Stilt（Himantopus himantopus）under the level II inhabiting water depth is significantly higher than that of the level I,and the step frequency is the opposite（P<0.05）,which may be related to the flexible change of foraging strategy.The foraging frequency of the Pied Avocet is the highest under level I inhabiting water depth and level H1 foraging water depth.With the increase of inhabiting water depth and foraging water depth,the foraging frequency of the Pied Avocet also increases.It shows that the deeper the water level is,the more difficult it is to forage and the less frequent it is to forage.The foraging frequency of the Black-tailed Godwit in the afternoon（14:00—17:00）is significantly higher than that in the morning（7:00—10:59）（P<0.01）,which is presumably related to the low temperature and frequent water fog weather in the morning during the non-breeding period in Poyang Lake.The Black-tailed Godwit prefers to forage under the water depths of level IV and V,while the Spotted Redshank prefers to forage under the water depths of level II and III.This is because the Spotted Redshank and the Black-tailed Godwit are similar in food resources and ecological habits,and the spatial niche overlap of foraging is relatively high.Therefore,they choose to forage under different inhabiting water depths to achieve niche separation.4.Habitat selection and utilizationIn this study,shorebirds mainly prefer shallow water area（83.85%）,followed by mudflat habitat（13.83%）,so the species similarity between shallow water area and mudflat habitat is also high（0.833）.There are 16 shorebirds with niche less than 0.200.This is because the habitat type is relatively simple,mainly living in shallow water area,the niche is relatively narrow,and most species have a high degree of niche overlap.The niche overlap of the Northern Lapwing and the Grey-headed Lapwing（Vanellus cinereus）with other shorebirds is less than 0.500,mainly due to the generalization of their foraging habits and the variety of food available for them in the habitat,which is more adaptive than other shorebirds.The water depth niche breadth of the six shorebirds is greater than 0.700,which may be because the shorebirds are generally small in body size and the corresponding habitat depth range is small,The depth niche overlap of Wood Sandpiper（Tringa glareola）and Dunlin（Calidris alpina）is the highest（0.876）,which is related to the similarity of their beak peak length and foraging habits.The preferred water depth range of Wood Sandpiper is 2.4—3.1cm,while that of Dunlin is 2.4—3.6 cm.Therefore,the competition among species in spatial niche is more intense.The proportion of mudflat habitat and the distance to the water area of Pied Avocet,Black-tailed Godwit,Spotted Redshank and Common Greenshank（Tringa nebularia）were significantly lower than those of Northern Lapwing.The proportion of shallow water area habitat and the distance to the mudflat were significantly higher than those of the Northern Lapwing.This is mainly related to the fact that the four shorebirds are animal-feeding birds and the Northern Lapwing is omnivorous birds.The main factors that affect the selection of foraging habitat of five shorebirds are food factors and safety factors.Therefore,for the protection of shorebirds’foraging habitat,it is necessary to have a certain water area and mudflat area to ensure that their food resources are relatively rich.Secondly,open areas with relatively low vegetation coverage are needed.In addition,efforts should be made to promote the reduction of human disturbance in birds’habitat to ensure their safety during foraging.