LANZHOU, Feb. 15 (Xinhua) -- A total of 871 whooper swans have been recorded during the ongoing wintering season in northwest China's Gansu Province, according to a recent survey.
Among the total, 157, or 18 percent, are adolescent swans, the highest ratio compared with that of three such surveys conducted from 2019-2021.
Since 2020, the number of wintering whooper swans in Gansu has exceeded 800 each year, said Zhang Lixun from the School of Life Sciences, Lanzhou University, who led the survey.
There are five major habitats in Gansu for the swans including two along the Yellow River, China's second-longest river, and the rest along three inland rivers.
According to Zhang, those wintering swans, mainly from Russia and Mongolia, gradually move southward to China every October and fly back to their original places in March of the following year.
"The number of wintering swans is directly related to the size of wetland in a region and the richness of edible grasses in the water," said Zhang.
More wintering whooper swans in Gansu indicates the continuous improvement of the ecological environment in west China, said Zhang.
The whopper swan is under second-class national protection. Gansu is one of the important habitats for the species, as well as a key monitoring region. ■