A heron flies over the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Herons rest at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

A heron flies over the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Birds frolic at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Birds rest at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Birds rest at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Birds are seen at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)

Birds rest at the Yongding River in Beijing Garden Expo Park in Beijing, capital of China, Jan. 21, 2021. (Xinhua/Li Xin)