Scaly-sided Merganser

Identification

The scaly-sided merganser is a striking duck with distinctive features that make it recognizable to keen observers. Both males and females sport a crest of wispy elongated feathers, reaching almost to the shoulders in adult males and being fairly short in females and immatures. The species' most characteristic feature is the scaled dark pattern on the flanks and rump, combined with a thin red bill. Adult males display a black head and neck, white breast and underparts, and blackish mantle and wings, except for white innerwings, with black scaling on the flanks. Females are more subdued in coloration, with a buffish head and grey replacing the male's black markings. Both sexes have orange-red legs and dark brown eyes.

Range & Habitat

This endangered species inhabits the temperate regions of East Asia, breeding in the Russian Far East (which supports approximately 85% of the global population), northeastern China's Changbai Mountains and Lesser Xingan Mountains, and possibly North Korea. The species is migratory, wintering in central and southern China, with smaller numbers scattered across Japan, South Korea, Taiwan, northern Vietnam, Myanmar, and Thailand. Scaly-sided mergansers favor mid-sized rivers that meander through wide expanses of mixed forest in mountainous terrain, typically at elevations up to 1,000 meters. They arrive on breeding grounds in March as winter ends and depart in mid-November with the onset of cold nights.

Behaviour & Diet

This shy and easily startled bird is largely solitary during breeding season, though small groups gather during autumn and winter migration—rarely exceeding a dozen individuals even on wintering grounds. Mergansers spend most daylight hours foraging along riverbed gravels, using their serrated beaks to catch prey. They are proficient divers, repeatedly submerging for quarter-to half-minute intervals with only brief pauses between dives, and in shallow water they submerge only their heads. During midday, they rest, preen, and socialize on riverbanks where they also sleep. Their diet is opportunistic and seasonal, consisting primarily of aquatic arthropods, frogs, and small to medium-sized fish. Stonefly and caddisfly larvae may constitute the bulk of their diet when available, while fish become more prominent as aquatic insect larvae hatch in summer. Preferred fish species include the dojo loach and lenok.

Best Time & Places to See It

Observing scaly-sided mergansers requires visiting pristine river systems within their breeding range during the breeding season from March through November. The Russian Far East, particularly the Primorye and South Khabarovsk regions, offers the best opportunities, as these areas support approximately 85% of the global population. During winter months, central and southern China's river systems, particularly tributaries of the Yangtze River, and South Korean rivers become reliable locations. However, travelers should be prepared for challenging conditions: these birds favor remote, primary forest rivers and are notoriously wary and easily startled, making them difficult subjects requiring patience and careful approach.

Photography Tips

Photographing scaly-sided mergansers demands discretion and patience. These shy birds startle easily, so approach slowly and quietly along riverbanks during their midday rest periods when they are more settled. Early morning and late afternoon foraging sessions offer opportunities to capture diving sequences, though the birds' habit of moving upriver when disturbed may work in your favor—position yourself upstream. The striking plumage contrast in males is best captured in good natural light, while the scaled patterns on flanks and rump require close detail shots to appreciate fully. Since groups are typically small and dispersed, particularly during breeding season, invest time in scouting pristine forest rivers and observing their daily routines before attempting photography.