Lake Tofutsu has long been known as a swan lake, and in early October, the "ko'oo" call begins to echo through the lake. Many of them migrate south, but some over-winter. When the lake's ice melts, they fly from their wintering grounds to their breeding grounds further north. Lake Tofutsu is rich in water plants, which serve as food for whooper swans, and the birds can be observed eating and drinking the water. During the severe winter season, whooper swans can be observed up close, although the number of swans is small.