Wild swans fly over a lake on the Yellow River Wetland in Pinglu, north China’s Shanxi province, Nov 6, 2014. Thanks to its better ecological environment, the wetland attracted more wild swans to spend winter in recent years.[Photo/Xinhua]

Wild swans fly over a lake on the Yellow River Wetland in Pinglu, north China’s Shanxi province, Nov 6, 2014. Thanks to its better ecological environment, the wetland attracted more wild swans to spend winter in recent years.[Photo/Xinhua]

Wild swans fly over a lake on the Yellow River Wetland in Pinglu, north China’s Shanxi province, Nov 6, 2014. Thanks to its better ecological environment, the wetland attracted more wild swans to spend winter in recent years.[Photo/Xinhua]

Wild swans fly over a lake on the Yellow River Wetland in Pinglu, north China’s Shanxi province, Nov 6, 2014. Thanks to its better ecological environment, the wetland attracted more wild swans to spend winter in recent years. [Photo/Xinhua]

Wild swans fly over a lake on the Yellow River Wetland in Pinglu, north China’s Shanxi province, Nov 6, 2014. Thanks to its better ecological environment, the wetland attracted more wild swans to spend winter in recent years.[Photo/Xinhua]