Mergus squamatus, a Chinese endemic species, national Class I key protected wild bird. It is the near threatened species worldwide and the winter bird in Sanqingshan. It is about 49-63 centimeters in body length, and its beak is flat with the tip pointing forward, which is different from the flat beak of any other species of Anatidae. Its beak and legs are red. The head and the upper part of the back of male bird are black, while the covering feathers in its lower part of back, waist and tail are white. There are white mirrors on its wings. The long feathers on its head stretch backward, forming double crests. In its side feathers, there are black scaly spots.