Diversity Of Wading Birds And Ecological Habits Of Some Species In Poyang Lake During Non-breeding Period

Diversity and ecological habit of wading birds were conducted in the Poyang lake during non-breeding period.The research contents involved diversity,behavioral time budget and rhythm,foraging behavior and habitat selection and utilization at multiple scales for wading birds.Our results are as following:Wading bird diversity:A total of 114402 individuals of birds belonging to 39 species of 9 families of 4 orders were recorded in five investigation regions of Poyang lake.Five species such as Siberian Crane Grus leucogeranus,White-naped Crane Grus vipio,Hooded Crane Grus monacha,Black Stork Ciconia nigra and Oriental Stork Ciconia boyciana,were listed in the first national key protected birds.Common crane Grus grus,Pheasant-tailed Jacana Hydrophasianus chirurgus,Little Curlew Numenius minutus,Eurasian Spoonbill Platalea leucorodia were listed in the second national key protected birds.The number of wading bird species accounted for 37.14%of the total number of wading bird species in the Poyang lake,indicating that the wading bird resources in our study area were rich and played an important role in the maintence of stucture and function of water bird diversity.Common crane,Pied Avocet Recurvirostra avosetta,Spotted Redshank Tringa erythropus,and Eurasian Spoonbill were stead dominant species in the Poyang lake.Pied Avocet and Spotted Redshank were the dominant species in our most study area,indicating these two species had wide distribution and high adaptation ability.In addition,drastic varation of number of species and individuals in each study area was detected.Annual variation of these parameters was also recorded in one region.These facts indicated that the adapatation of wading birds in the Poyang lake to variation of ecological factors such as water level and micro-habitats was weak.Behavioral time budget and rhythm:The main behaviors of small-sized wading birds such as Common Moorhen Gallinula chloropus,Spotted Redshank and Wood Sandpiper Tringa glareola were foraging.The main behaviors of Pheasant-tailed Jacana include foraging(41.64%)and resting(30.80%).The proportion of foraging for other three small-sized wading species was above 70%.Of the large-sized wading species,foraging behavior was the main behavior of Common Crane(57.86%)and Siberian Crane(72.11%).Foraging(38.80%)and resting(47.43%)were the main behaviors of Oriental Stork.Our results showed the foraging proportions of small-sized wading birds(Wood Sandpiper,Spotted Redshank and Common Moorhen)were further larger than that of large-sized wading species(Oriental Stork)with animal diet.Large-sized wading species such as Oriental Stork with animal diet had less foraging time than that of large-sized herbivorous Siberian Crane and Common Crane.The foraging behavior of Common Moorhen kept high proportion during the daytime and other behavior had low proportion and showed no obvious rhythm,which was different from that of other small-sized wading species such as Spotted Redshank and Pheasant-tailed Jacana.Spotted Redshank and Pheasant-tailed Jacana often foraged in the mixed group.So Pheasant-tailed Jacana increased their foraging behavior proportion when Spotted Redshank was resting.Thus these two species formed different foraging peaks and decreased their competiton.Both Siberian Crane and Common Crane kept the highest or higher foraging proportion in the morning and evening,which was the common strategy of other crane species during non-breeding period.The resting behavior of two cranes had a peak in the afternoon or noon because of the high temperature in the noon.And the cranes need short-time rest to restore their body strength after they had frequent foraging behavior in the morning.Foraging behavior:Pheasant-tailed Jacana,Wood Sandpiper,Spotted Redshank and Common Snipe Gallinago gallinago usually only foraged and had higher foraging frequency at low water lever grades.Thus they all had low adapatation to water level and were very sensitive to water level variation.Large-sized wading birds such as Eurasian Spoonbill,Common crane and Oriental Stork showed no significant difference in foraging frequency at different water depth.Siberian Crane had highest foraging success rates and success frequency at III grade water depth,indicating that the optimal foraging water depth of Siberian Crane was about 21.3 cm.This fact maybe related to food resources at III grade water depth.Common Snipe and Wood Sandpiper had higer foraging frequency in the morning(7:00—10:59)than that in the noon(11:00—13:59),perhaps because they had to increase their foraging frequency in the moring to compensate the energy expenditure at night.Oriental Stork,Siberian Crane and Common Crane showed no significant difference in foraging parameters at different time,indicating that light had no significant effects on foraging behavior of large-sized wading birds and also indicating that large-sized had relative stead energy requirement and intake rate during the daytime.The foraging success frequency(?~2=70.797,df=1,P=0.000)and success rates(?~2=5.356,df=1,P=0.020)of adult Siberian Crane were significantly higher than that of subadult cranes.Adult cranes had higher foraging ability and needed spend more energy to nurture and vigilance for subadults besides their own maintence energy.No significant difference in foraging frequency and foraging duration time was detected between adult and subadult cranes.This fact was opposite to the viewpoint that subadult cranes were lack of experience and had low foraging success rates and needed more foraging times to compensate their energy.The foraging water depth of adult cranes was significantly higher(?~2=50.945,df=1,P=0.000)than that of subadult cranes,which may be related to body size and foraging experience.Habitat selection and utilization:Wading birds mainly preferred to shallow water(53.90%)and grassland(19.72%),so bird similarity between shallow water and grassland was higher(0.706).The niche breadth of Northern Lapwing Vanellus vanellus(0.706)is the largest.Shorebirds had zero niche breadth because they only selected single habitat and mainly inhabit in shallow water or farmland.Both Spotted Redshank and Eurasian Spoonbill mainly foraged in shallow water and had highest niche overlap(0.959)of habitat utilization.Spotted Redshank was smaller than Eurasian Spoonbill.They often gathered to occupy different shallow water area,thus they had spatial niche separation to decrease competition and improve coexistence.Among large-sized wading birds,Oriental Stork preferred II grade water depth(about 8.31—16.70cm),and the selective rate ammounted to 59.38%.So Oriental Stork had narrower niche breadth(0.585),which may be related to foraging mode.The main habitat of Siberian Crane,Common crane and Oriental Stork was water area.The proportion of water area account for above 67%at different radius.The proportion of water area for Oriental Stork was from 81.55%to 99.54%.Farmland proportion for Siberian Crane and Common crane was relatively high because they liked to feed the winter bud in natural habitat and grain in farmland.The first principle component of all four large-sized wading birds(Siberian Crane,White-naped Crane,Common crane and Oriental Stork)was related to safety and food factors,indicating they all paid more attention to food resources and foraging environmental safety.Thus for the wading bird conservation we should decrease the effects of artifical disturbance on habitat of wading birds.We also should ensure a certain water area for Oriental Stork.Meanwhile we should left some grains in the farmland for herbivorous wading birds and ensure they had enough food to overwinter.