Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A flock of little swans fly over houses in the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A flock of little swans fly in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans fly in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A flock of little swans fly in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A flock of little swans fly at dawn in the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans fly in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A flock of little swans fly in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

A little swan flies in the sky at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 24, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering. (Photos: Xinhua)

Little swans fly over houses in the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.

Little swans are seen at the Donggu Lake wetland of the Quyuan administration area in Yueyang City, central China's Hunan Province, Nov. 23, 2021. About 3,000 little swans have arrived at the Donggu Lake wetland of the Quyuan administration area in Yueyang for wintering.