An egret is seen at a Yellow River wetland in Zhaodu Town of Dali County, northwest China's Shaanxi Province, Nov. 21, 2019. (Xinhua/Shao Rui)

An egret flies over a Yellow River wetland in Zhaodu Town of Dali County, northwest China's Shaanxi Province, Nov. 21, 2019. (Xinhua/Shao Rui)

Wild birds fly over a Yellow River wetland in Fanjia Town of Dali County, northwest China's Shaanxi Province, Nov. 21, 2019. (Xinhua/Shao Rui)

Egrets are seen at a Yellow River wetland in Fanjia Town of Dali County, northwest China's Shaanxi Province, Nov. 21, 2019. (Xinhua/Shao Rui)