A heron forages at Hainan Xinying Mangrove National Wetland Park in Danzhou City, south China's Hainan Province, Jan. 18, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.(Xinhua/Yang Guanyu)

A flock of birds rest at Xinyingwan mangrove nature reserve in Danzhou, south China's Hainan Province, Jan. 19, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.(Xinhua/Yang Guanyu)

A black-faced spoonbill flies in Panshan Village of Xinzhou Town in Danzhou City, south China's Hainan Province, Jan. 19, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.

A black-faced spoonbill forages in Panshan Village of Xinzhou Town in Danzhou City, south China's Hainan Province, Jan. 19, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.(Xinhua/Yang Guanyu)

A spoon-billed sandpiper forages at Xinyingwan mangrove nature reserve in Danzhou City, south China's Hainan Province, Jan. 19, 2021.(Xinhua/Yang Guanyu)

Two lesser sand plovers fly in Hainan Xinying Mangrove National Wetland Park in Danzhou City, south China's Hainan Province, Jan. 18, 2021.(Xinhua/Yang Guanyu)

Black-faced spoonbills rest at Dongzhaigang National Nature Reserve in Haikou, south China's Hainan Province, Jan. 13, 2021.(Xinhua/Yang Guanyu)

A flock of herons fly in Panshan Village of Xinzhou Town in Danzhou City, south China's Hainan Province, Jan. 19, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.(Xinhua/Yang Guanyu)

Black-winged stilts are seen at a wetland in Qiugang Village of Ledong Li Autonomous County, south China's Hainan Province, Jan. 17, 2021.(Xinhua/Yang Guanyu)

A lesser sand plover forages at Xinyingwan mangrove nature reserve in Danzhou, south China's Hainan Province, Jan. 19, 2021.(Xinhua/Yang Guanyu)

A greater sand plover rests at Xinyingwan mangrove nature reserve in Danzhou City, south China's Hainan Province, Jan. 19, 2021.(Xinhua/Yang Guanyu)

Black-faced spoonbills rest at Dongfang black-faced spoonbill nature reserve in Dongfang City, south China's Hainan Province, Jan. 18, 2021.(Xinhua/Yang Guanyu)

Herons rest in Panshan Village of Xinzhou Town in Danzhou City, south China's Hainan Province, Jan. 19, 2021. South China's Hainan Island has launched a survey of waterbirds wintering across the island, covering 50 coastal habitats of waterbirds, to better understand their species, numbers and distribution.(Xinhua/Yang Guanyu)