Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)

Black-necked cranes are seen at the Dashanbao Black-Necked Crane National Nature Reserve in Zhaotong, southwest China's Yunnan Province, March 22, 2013. Dashanbao Reserve is the biggest wintering habitat for black-necked cranes in China. (Xinhua/Liang Zhiqiang)