This duck visits reservoirs and lakes in mountainous area of Mie in winter. The bird is rather shy, and stays under tree shade, and seldom comes to open water. The drake has showy plumage, and sometimes fights against other males for female.

The duck prefers acorns for food in winter. Winter population is about 10,000 in Japan according to the nation-wide foul count. However, the size of the breeding population in Japan is not known, and seems very small. Most of the bird comes from northeastern China.

The main breeding areas in Japan are Hokkaido, Northern Honshu and high elevations in central Japan. However, a small number of breeding pairs are recorded in Mie. During breeding male losses the showy winter plumage, and is similar to female.

This duck uses a hole of trunk of tall tree as a nest, and chicks dive down onto the ground or on the water. The chicks are enough bulky for soft landing. So pond or stream is indispensable for feeding and safety of the chicks. Therefore, presence of big tree with a hole near water is a limiting factor of the breeding of this species.