What kind of wild bird is the whooper swan? With a total length of 140 cm, it is one of the largest birds in Japan. It makes a loud, echoing call: "Koo, koo." They migrate to Lake Tofutsu and Lake Tsuru. When these lakes freeze over, most of the flock migrates to southern areas, but some overwinter at Lake Mokoto and near the mouth of the Tomobetsu River. D0901