Black-necked cranes rest on the Doqen Co (Lake) in Yadong County, southwest China's Tibet Autonomous Region, May 29, 2019. (Xinhua/Zhang Rufeng)

Black-necked cranes forage on the Doqen Co (Lake) in Yadong County, southwest China's Tibet Autonomous Region, May 29, 2019. (Xinhua/Zhang Rufeng)

Black-necked cranes fly over the in Doqen Co (Lake) Yadong County, southwest China's Tibet Autonomous Region, May 29, 2019. (Xinhua/Zhang Rufeng)

Black-necked cranes rest on the Doqen Co (Lake) in Yadong County, southwest China's Tibet Autonomous Region, May 29, 2019. (Xinhua/Zhang Rufeng)