A flock of wild geese and several wild ducks are seen at the Yeya (Wild duck) Lake Wetland Reserve in the suburb of Yanqing District of Beijing, capital of China, March 20, 2018. A large number of birds fly to the wetland as the weather gets warmer in Beijing. (Xinhua/Li Xin)

Grey cranes fly over the Yeya (Wild duck) Lake Wetland Reserve in the suburb of Yanqing District of Beijing, capital of China, March 20, 2018. A large number of birds fly to the wetland as the weather gets warmer in Beijing. (Xinhua/Li Xin)