Swans are seen at the Caofeidian wetland in Tangshan, north China's Hebei Province, Feb. 25, 2023.

The Caofeidian wetland, located in the city of Tangshan, is an important habitat for the migratory birds. (Xinhua/Yang Shiyao)

Swans fly over the Caofeidian wetland in Tangshan, north China's Hebei Province, Feb. 25, 2023.

The Caofeidian wetland, located in the city of Tangshan, is an important habitat for the migratory birds. (Xinhua/Yang Shiyao)

Swans are seen at the Caofeidian wetland in Tangshan, north China's Hebei Province, Feb. 25, 2023.

The Caofeidian wetland, located in the city of Tangshan, is an important habitat for the migratory birds. (Xinhua/Yang Shiyao)

Swans are seen at the Caofeidian wetland in Tangshan, north China's Hebei Province, Feb. 25, 2023.

The Caofeidian wetland, located in the city of Tangshan, is an important habitat for the migratory birds. (Xinhua/Yang Shiyao)

Swans are seen at the Caofeidian wetland in Tangshan, north China's Hebei Province, Feb. 26, 2023.

The Caofeidian wetland, located in the city of Tangshan, is an important habitat for the migratory birds. (Xinhua/Yang Shiyao)