Flock of Black-necked Crane Wintering at Napahai Nature Reserve,China
云南省纳帕海自然保护区越冬黑颈鹤的集群特征

From October 2004 to May 2005, flock size and composition of wintering black-necked cranes(Grus nigricollis) were studied using spot scanning technique at Napahai Nature Reserve in Yunnan province.At night, the mean wintering population size was 67.9(16-157, n=17).Composed by common crane(Grus grus) or not, roost cranes were divided into sing-species flock and mixed-species flock.The numbers of crane in sing-species flock were 65.3% of total black-necked cranes.In the day, feeding flocks were classified into three types:family group comprised of breeding pair and their offspring ranging between two to four;sub-adult flock composed mainly by sub-adults ranging between three to 65 with an average size of 16.1(n=1017);special flock composed by single cranes.Black-necked crane flocks were affected by season, temperature, breeding status, food abundance and availability, and their sizes changed significantly in daytime or between different months(P=0.000<0.05).After family breakup happened in late March, Juveniles were drove away by their parents and then they got together to join the sub-adult flocks.