The scaly-sided merganser or Chinese merganser (Mergus squamatus) is an endangered typical merganser (genus Mergus). It lives in Manchuria and extreme Southeast Siberia, breeding in the north and wintering in the south.
This striking sea duck has a thin red bill and a scaled dark pattern on the flanks and rump. Both sexes have a crest of wispy elongated feathers, reaching almost to the shoulders in adult males and being fairly short in females and immatures. The adult male has a black head and neck, white breast and underparts, and blackish mantle and wings, except for the white innerwings. The scaling is also black, while the tail is medium grey. The female has a buffish head and otherwise replaces the male's black with grey colour. The legs are orange-red and the irides dark brown in both sexes.