A swan is pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans fly over the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Xu Qin)

Swans are pictured at the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Lian Zhen)

Swans fly over the Ulan Suhai Lake in Bayan Nur, north China's Inner Mongolia Autonomous Region, Oct. 28, 2020. (Xinhua/Xu Qin)