Swans are seen on the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Swans are seen on the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Avocets are seen on the Qili Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. [Photo/Xinhua]

Swans are seen on the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Wild Geese are seen on the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter. [Photo/Xinhua]

Wild Geese fly over the Longmiao Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Swans fly over the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Swans fly over the Mao’er Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter.[Photo/Xinhua]

Wild Geese fly over the Longmiao Lake in Xuyi county of Huai’an, East China’s Jiangsu province, Nov 29, 2015. A great many birds have migrated to the wetlands in the county to overwinter. [Photo/Xinhua]