Ruddy shelducks fly above the Lhasa River in southwest China's Tibet Autonomous Region, Dec. 5, 2010. (Xinhua/Lhaba Cering)

A ruddy shelduck flies above the Lhasa River in southwest China's Tibet Autonomous Region, Dec. 5, 2010. (Xinhua/Lhaba Cering)

A bird flies above the Lhasa River in southwest China's Tibet Autonomous Region, Dec. 5, 2010. (Xinhua/Lhaba Cering)

Ruddy shelducks fly above the Lhasa River in southwest China's Tibet Autonomous Region, Dec. 5, 2010.QQQwww.Chinakindnesstour.com

Tens of thousands of migratory birds have flown to the Lhasa River wetland recently to spend their winter days. QQQwww.Chinakindnesstour.com