Diversity of waterbirds and change in home range of bar-headed geese Anser indicus during breeding period at Hangcuo Lake of Tibet, China
西藏夯错水鸟多样性及斑头雁繁殖活动区的变化

A survey on current status of waterbirds was conducted at Hangcuo Lake of Tibet from April to November of 2009, to help strengthen the wetland conservation and management and establish baseline information for the surveillance of avian influenza at Hangcuo Lake. A total of 26 waterbird species, belonging 10 families and 6 orders, were recorded during the survey. Over three thousands of Bar-headed Geese Anser indicus and Brown-headed Gulls Larus brunnicephalus were found breeding on the small island in the lake, suggesting Hangcuo Lake is an important breeding area for Bar-headed Geese and Brown-headed Gulls. With the highest diversity of waterbird species, especially remarkable increases in duck species and numbers, April and October were two peak periods for spring and fall migrations of waterbirds at Hangcuo Lake, respectively. Satellite tracking on the Bar-headed Geese showed that the geese mostly foraged in Hangcuo Lake and the surrounding wetlands in the early breeding period. In the mid-breeding period, the home range decreased dramatically, because the birds were spending much time in sitting on the nests. After the chicks were hatched, adult geese together with their fledglings, left Hangcuo Lake for other wetlands for foraging and chick-rearing. That movement by goose families after hatching possibly was due to decreasing food resources at Hangcuo Lake and resulted in a larger home range in the late breeding period comparing to the mid-breeding period. By the time just before the fall migration started, the numbers of Bar-headed Geese increased remarkably again, as a result of many Bar-headed Geese coming back from nearby wetlands and immigrating from the north to Hangcuo Lake. Hangcuo Lake had fewer number of waterbird species than Qinghai Lake, most likely due to the high altitude, strong ultraviolet radiation, dry weather, and poor habitat diversity of vegetation communities at Hangcuo Lake.