Preliminary Study On The Waterbirds Community And The Behavior Of The Mixed-Species Bird Flocks In Shanxinsha Island,Guangxi

During March-April 2018,September-December 2018 and January 2019,the seasonal waterbirds composition were studied in Shanxinsha Island,Guangxi.In addition,the behaviors of two threatened species,Calidris pygmeus and Calidris tenuirostris,were observed to understanding the interspecific relationship and co-existence mechanism in the mixed-species bird flocks.The results were as follows:1.The waterbird communityUsing the maximum retention method,a total of 20417 waterbirds,belonging to 51 species,7 families and 2 orders,were recorded in Shanxinsha Island.Among them,1 species,Tringa guttifer,was classified as nationally protected in China and 4 were listed in the IUCN Red List.It included 1 Critically Endangered,Calidris pygmeus;2 Endangered,Calidris tenuirostris and Tringa guttifer;and 1 Vulnerable species,Saundersilarus saundersi.From spring to winter,the three waterbirds are dominant species of the Shanxinsha Island,and the number of individuals exceeds 10% of the total number of waterbirds,namely,the Charadrius alexandrinus,the Chrardrius mongolus and the Chroicocephalus ridibundus.The focus of this study was Calidris pygmeus and Calidris tenuirostris.In the autumn,the number of Calidris pygmeus and Calidris tenuirostris was the highest,especially the Calidris pygmeus,which identified seven individuals recorded a day in November.This record is already more than 1% of the total number of the Calidris pygmeus.It is indicated that theShanxinsha Island is an indispensable and important migration resting place for the Calidris pygmeus.2.The mixed-species bird flocks in Shanxinsha IslandBecause of the fluctuation of tide,birds in Shanxinsha Island can be divided into two different stages of activity: cluster rest stage and scattered foraging stage.The cluster analysis method was used to analyze the mixed-species bird flock of Shanxinsha Island in two active stages.In the cluster rest stage,the composition of mixed-species bird flocks are closely related to their body type,which can be divided into three groups: the small-body mixed-species bird flocks,the middle-body mixed-species bird flocks and the large-body mixed-species bird flocks.In the scattered foraging stage,in order to study the mixed rule of waterbirds,foraging sites were divided into four different microhabitats: Waterless Beach,Waterlogged beach,Tidal channel and Tidal beach.The results of cluster analysis of frequency of microhabitat of waterbirds were approximately the same as the statistical results,and the mixed-species bird flocks could be formed more easily if the utilization of microhabitats in foraging areas was similar.3.A study on the mixed-species bird flocks behavior of the Calidris pygmeus.We mainly discuss the behavior of the Calidris pygmeus in the cluster rest stage.The position of the Calidris pygmeus in the small-body mixed-species bird flocks during the cluster rest stage is deviated to the center.In the small-body mixed-species bird flocks,the Calidris pygmeus has a choice of objects close to each other.There is more than 50% chance of getting close to Chrardrius mongolus.The mixed-flock strategy adopted by the Calidris pygmeus during the rest is consistent with the risk dilution hypothesis and the collective detection hypothesis.4.A study on the mixed-species bird flocks behavior of Calidris tenuirostris.The community characteristics of the mixed-species birds flocks added in the scattered foraging process of the Calidris tenuirostris were mainly discussed in this paper.And the benefits gained in mixed-species bird flocks in the scattered foraging phase.In the scattered foraging stage,the Calidris canutus is the most common species in the mixed group.Theforaging frequency and the moving rate were independent of the total number of birds in the mixed-species bird flocks.There was a significant correlation between the flight initiation distance and the number of birds in the mixed-species bird flocks.And the more the number of birds,the further the flight initiation distance was.It is consistent with the early warning hypothesis.