Migratory birds in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. Different kinds of aerial birds, such as black-headed gulls, red-crowned cranes, and bar-headed geese, have been arriving since November and will head for the north in March. [Photo by Jigmed Wangtso /chinadaily.com.cn]

Aerial birds swim in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Jigmed Wangtso /chinadaily.com.cn]

Bar-headed geese in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Daqiong/chinadaily.com.cn]

Bar-headed geese congregate in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Daqiong/chinadaily.com.cn]

A bird captures its dinner in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Jigmed Wangtso /chinadaily.com.cn]

Birds come in for a water landing in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Jigmed Wangtso /chinadaily.com.cn]

Bar-headed geese in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Daqiong/chinadaily.com.cn]

Bar-headed geese in the valley of Lhasa River, Southwest China's Tibet autonomous region, Dec 22, 2016. [Photo by Daqiong/chinadaily.com.cn]