A grebe is seen at the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)

Tourists ride at the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)

Birds fly over the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)

A black-headed gull flies over the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)

Birds are seen at the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)

A heron flies over the Beijing Wild Duck Lake Wetland in the suburban Yanqing District of Beijing, capital of China, April 5, 2020. (Xinhua/Chen Zhonghao)