
Photo taken on Nov. 14, 2018 shows a gull at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Photo taken on Nov. 14, 2018 shows the migrant birds at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Grey cranes are seen at Duchang wetland of Poyang Lake, east China's Jiangxi Province, Nov. 14, 2018. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Photo taken on Nov. 9, 2018 shows migrant birds at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Migrant birds are seen at Duchang wetland of Poyang Lake, east China's Jiangxi Province, Nov. 14, 2018. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Aerial photo taken on Nov. 9, 2018 shows migrant birds at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Grey cranes are seen at Duchang wetland of Poyang Lake, east China's Jiangxi Province, Nov. 14, 2018. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Grey cranes are seen at Duchang wetland of Poyang Lake, east China's Jiangxi Province, Nov. 14, 2018. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Aerial photo taken on Nov. 9, 2018 shows grey cranes at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)

Aerial photo taken on Nov. 9, 2018 shows migrant birds at Duchang wetland of Poyang Lake, east China's Jiangxi Province. The Poyang Lake, China's largest freshwater lake, saw a flock of migratory birds overwintering in it. (Xinhua/Fu Jianbin)