Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. (Photos: Xinhua)

Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.

Migratory birds are seen at the Longwangtan Park in Lhasa, southwest China's Tibet Autonomous Region, Nov. 21, 2019. Many migratory birds, such as bar-headed geese and black-headed gulls, arrived in areas along the Lhasa river valley and the Yarlung Zangbo River to escape the cold.