关键词: 灰鹤, 白枕鹤, 鄱阳湖, 集群特征, 年龄结构

Abstract: Surveys were conducted from October 2012 to April 2013 of common cranes (Grus grus) and white-naped cranes (Grus vipio) wintering in the Poyang Lake for population size, distribution and flocking features, as well as age composition of the common cranes. The maximum number of common crane individuals in one entry of record was 599 and of white-naped crane individuals was 600.Common crane populations were observed and recorded in 18 of the 34 lakes (or farmland) surveyed in four nature reserves, and peaked in size during the period from January to early March and 62.87% of the population gathered in Bashazhou Nature Reserve in Boyang County. White-naped cranes were observed and recorded in 12 of the 34 lakes (or farmlands) surveyed in four nature reserves and peaked in population size from late February to early March and 95.77% of the population were found in Poyanghe Nature Reserve. Comparison with the records of the past years reveals that changes happened in major gathering area of common cranes, but nothing did with white-naped cranes. The mean size of flocks of common cranes and of white-naped cranes was 8.50±19.84 (n=148) and 7.52±21.47 (n=63), respectively, indicating no significant differences between the two species in any wintering periods (P>0.05). The flocks of common cranes were mostly family-based ones, which accounted for 70.07%, and flocks of individual gathering was the second, accounting for 23.36%. The flocks of families were mostly composed of families of two adults plus one offspring, each, which accounted for 46.88%. The flocks of individual gathering were often composed of 5 – 9 individuals each, which accounted for 71.88%. The mean flock size of the former was 2.76±0.69 (n=96) and of the latter 13.84±20.82 (n=32). The two types of flocks did not change much in size with time period (P>0.05). In the flocks of common cranes, juveniles accounted for 20.21%. In light of the situation in the Poyang Lake, some corresponding measures arehave been proposed for protection of the two species of cranes therein.

Key words: common crane, white-naped crane, Poyang Lake, group characteristic, age composition