Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Aerial photo taken on March 10, 2018 shows a first-level state protected wildlife black-necked crane in Linzhou County, southwest China's Tibet Autonomous Region. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Aerial photo taken on March 10, 2018 shows the first-level state protected wildlife black-necked cranes in snow and water in Linzhou County, southwest China's Tibet Autonomous Region. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)

Black-necked cranes, the first-level state protected wildlife, are seen in snow in Linzhou County, southwest China's Tibet Autonomous Region, March 10, 2018. Tibet is currently temporary home to more than 8,000 black-necked cranes.(Xinhua/Purbu Zhaxi)