Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes wander at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes fly at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes fly at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)

Black-necked cranes fly at Napa Lake Nature Reserve in Shangri-la in Deqen Tibetan Autonomous Prefecture, southwest China's Yunnan Province, March 21, 2016. Thanks to protection and restoration at Napa Lake Nature Reserve, more black-necked cranes choose to spend winter here with the number rising from 300 to 400 within a couple of years. (Xinhua/Lin Yiguang)