Population changes of wintering Black-necked Crane (Grus nigricollis) along the upper-middle valley of Yarlung Zangbo

During the period of 2007-2014, eight surveys were conducted at the upper-middle valley of Yarlung Zangbo. Following are the results: 1) The average population size of the wintering Black-necked Crane (Grus nigricollis) at the upper-middle reaches of Yarlung Zangbo valley was 1,541±227. From 2007 to 2010, the population size decreased and in 2010-2013, it increased; then the population decreased in 2014. 2) The total wintering Black-necked Crane population size in this region was positively correlated to the Black-necked Crane population at south of the valley(P<0.01, r=0.928). The population size in the north was less than the south, but the stability was higher than the south. 3) The wintering Black-necked Cranes moved in flocks, while the family and individual form is rarely seen in the winter season. Most crane families were composed of two adults with 1-2 young birds, however, we did observe two adults with three young cranes. 4) From the eight surveys and the statistical analysis, the largest crane flock had 375 birds during the surveys. 5) In 2014, the Black-necked Cranes used 79.14% of the stubble land, 3.73% of the cultivated land, 0.76% of the winter wheat land, and 16.37% of the others.