The Chinese Merganser, or Scaly-sided Merganser, Mergus squamatus, is a typical merganser.

This is a striking duck with a shaggy crest and scaled flanks. The adult male has a black head and neck with a long crest, white breast and underparts, and blackish mantle with white innerwings. The female has a buffish head and a wispy crest.

Their breeding habitat is rivers in primary forest in south-east Russia, North Korea and north-east China. They are migratory, wintering in central and southern China, with small numbers in Japan, South Korea, Taiwan, northern Vietnam, Myanmar and Thailand.

This species is endangered. Numbers reduced in the 1960s and 1970s due to alterations to primary forests along major rivers. Current threats included illegal hunting, entanglement in fishing nets and river pollution. According to the IUCN classification EN C1, less than 2500 adult birds remain, and numbers are expected to decline by no less than 20% until around 2010 (BirdLife International 2006).

A confounding factor is that this species is rather solitary. Pairs generally avoid each other, and even on the wintering grounds, groups of more than a dozen are very rare. Thus, even though it is known to occur over a wide area, an accurate estimate of its population is difficult. A somewhat crude but nonetheless important indication of the Scaly-sided Merganser's population status may be gleaned by annual censuses on the lower Yangtze River, which constitutes the single most important wintering area known to date (Fen-Qi et al. 2002).