A flock of pied avocets are seen at the East Dongting Lake National Nature Reserve, central China's Hunan Province, Feb. 25, 2016. Migratory birds have prepared to fly back to the north as the weather warms up here. It is surveyed that more than 120,000 birds lived through the 2015-2016 winter in the East Dongting Lake region, 18,000 more than last year. (Xinhua/Li Ga)