Preliminary Study On Wintering Ecology Of Siberian Crane And Common Crane In Poyang Lake

Poyang Lake is an important wetland in the East Asian-Australian Flyway that inhabits a large number of cranes.The author has done some studies on population distribution,group characteristic,age structure,habitat selection,behavior of Common crane(Grus Grus)and Siberian crane(Grus leucogeranus)in Poyang Lake during the winter periods from 2017 to 2020.The results showed as following:(1)Population distribution,group and age characteristics: January of the three years from 2018 to 2020,populations of both Common crane and Siberian crane firstly decreased,then increased.From 2017 October to 2018 March,the mean group size was 29.80±76.02 individuals for the Common crane.The group size of Common cranes in the early and late wintering periods was significantly lower than that in the middle period,and that in the late wintering period was the smallest.The group size of Common crane in artificial habitat was larger than that of natural habitat,was related to food resources..Within the family group,the proportion of two adults with one juvenile was the highest.The percentage of juvenile of Common crane was all higher than 20% in the three overwintering periods.Juvenile proportion of natural habitat was lower than that in artificial habitat.The mean group size was 36.05±73.13 individuals for the Siberian cranes.The group size of Siberian cranes in the middle and late wintering period was significantly higher than that in the early period,the group size of Siberian crane in artificial habitat was both larger than that of natural habitat.The proportion of juveniles in natural habitat of Siberian crane is higher than that in artificial habitat.(2)Habitat selection of Siberian cranes and Common cranes was studied in Poyang Lake at both landscape and micro-habitat scales,from winter period during 2018—2019 and 2019—2020.At landscape scale,the main habitats of Common cranes include waters and farmlands.Proportions of village,roads and shoals of Common cranes habitat have significantly difference from that in control plots.At the micro-habitat scales,the distance between the habitat of Common crane and village were significantly further than in control quadrats.Principal component analysis showed that interference factor,food and safety factor were the two important factors.The main habitats of Siberian cranes include waters and farmlands,too.Proportions of village,roads and water area of Siberian cranes habitat have significantly difference from that in control plots.At the micro-habitat scales,the distance between the habitat of Siberian crane and village were also significantly further than in control quadrats.Principal component analysis showed that interference factor,safety and food factor were important in the two principal components.(3)The wintering time budget and behavior rhythm of Siberian crane inhabiting lotus pond reclamation area of Poyang Lake were observed by instantaneous scan during the wintering period of 2016-2017 and 2019-2020.Major behaviors included foraging,vigilance,grooming,and resting.Adult vigilance was significantly greater than juveniles vigilance,while adult foraging was significantly less than juveniles foraging.Foraging behaviors of adults in family groups were significantly lower than those of adults in non-family groups were.Cranes maintained high foraging frequencies in each period,with 2 peaks during the daytime.The proportion of adults and juveniles foraging increasing or decreasing at similar times.During each time period,the proportion of adults performing vigilance or grooming behaviors was greater than that of juveniles.The grooming behavior of adult and juveniles both peaking between 14:00 and 14:59.(4)During the wintering period of 2018-2019 and 2019-2020,we observed the daily wintering behavior patterns and their effects in the Common crane.This was done using instantaneous scan and focal sampling methods with Common cranes in Poyang lake.Foraging,vigilance,grooming and locomotion were the cranes' main behaviors.The time budget and duration spent foraging by juvenile cranes was significantly greater than that of adult cranes.The time budget,frequency and time budget of vigilance in adult cranes during foraging intervals were all significantly greater than that of juvenile cranes.The predominant patterns of Common cranes which inhabiting artificial habitat is difference from that natural habitats.The main diurnal behaviors also varied significantly between different artificial habitat and natural habitats.The duration and time budget of foraging behaviors increased throughout the overwintering period.Locomotion was increased throughout the wintering period,which was related to the availability of food resources.In terms of the activity rhythms,foraging behavior was always at a high level during the daytime,with two small peaks.A peak in grooming behavior occurred after a peak of foraging behavior.The peak of vigilance behavior in young cranes occurred in the trough of adult cranes?(5)From October 2018 to March 2019,the focus animal method was used to study on the foraging and vigilance behaviors of Common crane in Poyang lake.Mean foraging frequency was(7.02±6.78)times /min.Mean step rate was(9.5±2.98)steps /min.Family type had significant effects on the step rate,the phenomenon is related to the amount of food resources each group owns.Mean vigilance frequency was(0.42±0.55)times /min.The frequency of vigilance behavior for juvenile cranes was significantly lower than adult cranes because the juvenile cranes need more time to forage and have lower ability to detect threats.