Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)

　　Wild mandarin ducks are seen on the Xin'an River in Huangshan City, east China's Anhui Province, Nov. 16, 2018. The Xin'an River in recent years has seen an increasing number of wild mandarin ducks overwintering in it. (Xinhua/Shi Guangde)