| Black-necked crane annually migrate from the breeding sites to Wumeng Mountain area where located in Northeastern Yunnan and Northwestern Guizhou for overwintering,and wetland Caohai can be served as one of the largest overwintering site within this area.As we known,the adaptive habitats are critical for the survivals of overwintering migrating birds,The overwintering habitat of Black-necked Cranes consists of foraging grounds and roosting sites,in which roosting sites are often fixed and specialized.But,due to the rapid expansion of urbanization,and boom of local population,the crane's habitat is suffered from the increasing disturbance of human,especially the water level of Caohai is planning rising up,so it can be presumed the crane's habitat for overwintering would be influenced deeply.Therefore,in this paper,the instantaneous scanning behavior observation and sampling methods are used to to understand the habitat selection mechanism of roosting sites and behavior of Black-necked Cranes,and promote conservation and management of Black-necked Cranes overwintering in Caohai.The results of the study are reported as follows:1.The results showed that both departure and return times were significantly different between the three periods.A field study by means of instantaneous scan sampling was conducted on the flight and behavior patterns of Black-necked Cranes at seven roosting sites at the Caohai wetland.The results showed that the time of Black-necked Cranes department of the roosting site was significantly different in different periods of overwintering(P < 0.01).There was significant difference in the time of return to the roosting site(P < 0.05).Compared with the early winter,the departure time from roosting sites were delayed in middle winter and advanced in late winter(mean times: 7:38,7:45,7:14),while the return time to roosting sites became gradually later throughout the winter(mean times:17:54,18:07,18:22).2.There was a significant difference in Black-necked Crane behavior before departure between early,mid,and late winter(P < 0.01),and the behavioral differences after the return to the roosting site were also significant(P < 0.01).Crane behavior before the morning departure and after the evening return in the early winter period was significantly different(P < 0.01),as was the crane morning and evening behavior in the mid-winter period(P < 0.01),and late winter period(P < 0.01).For the 80-minute period before the morning departure from the roosting site,maintaining(34.32%)and resting(32.38%)were the dominant behaviors,while foraging(43.04%)and resting(23.68%)were the dominant behaviors within the 90-minute period after the evening return.3.The departure times were significantly related with sunrise time(r = 0.832,n = 48,P <0.01),while the return times were significantly but weakly correlated with sunset time(r = 0.353,n = 47,P < 0.01).The difference between the sunrise time and the crane departure time(Y1)is affected by humidity at the time of the departure(W).(Y1 = 0.469? 0.625 W,P < 0.05).The difference between the sunrise time and the crane departure time(Y1)is inversely proportional to humidity at the time of departure(W).The difference between the sunset time and the crane return time(Y2)is affected by mean daily temperature(T).(Y2 = 1.231?0.107 T,P < 0.05).4.Fifteen habitat factors of Blank-necked Cranes were investigated by sampling method,and Person correlation analysis was used.The index of resource selection and the resource selection function were used to analyze 74 habitats of Blank-necked Cranes and 74 non-roosting areas.The results showed that Black-necked Cranes were selective to eight habitat factors.The resource selection function of roosting habitat of Blank-necked Cranes is as follows:Logistic(P)=1.243-4.105×mountain height+8.397×vegetation height of shoal-7.999×vegetation height of sample+1.584×visible range area.Roosting sites are the key factor for the black-necked crane to survive in the winter in Caohai.Based on the observation of the behavior rhythm of roosting site of Blank-necked Cranes in the Caohai and the analysis of the habitat factors influencing roosting sites,we have understood well the roosting habitat selection of Black-necked Cranes in Caohai. |
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