Red-breasted Merganser

Identification

The red-breasted merganser is a sleek diving duck measuring 51–64 cm in length with a distinctive spiky crest and long, thin red bill edged with serrated projections. Males are more striking, weighing slightly more than females at 950–1,350 g compared to 800–1,100 g. In breeding plumage, males display a dark head with a green sheen, white neck, rusty-red breast, black back, and white underparts—a combination that gives the species its common name. Females and juveniles are more subdued, with rusty heads and greyish-brown bodies; juveniles can be distinguished by their shorter crests and smaller white wing patches.

Red-breasted mergansers overlap considerably with the similar common merganser, which can make identification challenging outside breeding season. However, females and non-breeding birds can be distinguished by subtle features: the red-breasted merganser lacks the sharp contrast between head and breast seen in female common mergansers, and females lack the light chin patch characteristic of that species.

Range & Habitat

This species is native to much of the temperate to subarctic Northern Hemisphere, with breeding habitat spanning freshwater lakes and rivers across northern North America, Greenland, Europe, and the Palearctic. Red-breasted mergansers are highly migratory, with northern breeders wintering in coastal waters further south—a pattern that makes them the most frequent merganser species to regularly inhabit saltwater environments. Notably, populations in parts of northwestern Europe with oceanic climates, including Iceland, Ireland, Britain, Norway, and Baltic Sea islands, tend to be largely resident or disperse only short distances.

The species nests in sheltered locations on the ground near water, often (though not always) close to estuaries or sea coasts. While their range broadly overlaps with the common merganser, red-breasted mergansers show a preference for saltwater habitats compared to their freshwater-loving cousins, though overlap between the species is frequent.

Behaviour & Diet

Red-breasted mergansers are highly active hunters, flying rapidly and diving from the surface to pursue prey underwater. The serrated edges of their bills are specifically adapted to grip slippery fish, which form their primary diet, though they also consume aquatic insects, worms, crustaceans, and amphibians. Their feeding strategy is distinctly different from dabbling ducks, relying on pursuit diving to catch moving prey.

During breeding season, males perform a highly stereotypic courtship display starting in mid-November and continuing until June or occasionally July. This involves synchronized neck stretching, bending, and contracting movements performed while swimming, with males fanning and straightening their crests. Females watch nearby and actively select mates, sometimes chasing or attacking males. Outside the breeding season, the species is largely silent, though females produce a rasping "prrak prrak" during courtship and a harsh "gruk" in flight, while males emit a distinctive catlike meow.

Best Time & Places to See It

The red-breasted merganser is widespread and common, though viewing opportunities vary by location and season. In regions with migratory populations, birds are present during breeding season on northern lakes and rivers, while coastal areas host greater concentrations during winter months and migration periods. Autumn migration flocks tend to be larger than those seen during spring migration. In northwestern Europe—particularly around Iceland, Ireland, Britain, Norway, and the Baltic—populations may be observed year-round, as these largely resident birds remain through winter.

For the best viewing experience, focus on coastal waters during winter and on freshwater lakes and river systems during breeding season. Outside the breeding season, the species forms flocks that can provide excellent viewing opportunities, particularly in coastal wintering grounds.

Photography Tips

Photograph males during breeding plumage to capture their distinctive coloration: the glossy green head, white neck, and rusty breast provide striking contrasts. The species' rapid flight requires fast shutter speeds, so be prepared with appropriate camera settings when birds are in motion. The serrated red bill is a signature feature worth highlighting in close-up shots.

Given their preference for saltwater habitats and tendency to form flocks during migration and winter, coastal locations during these seasons offer excellent opportunities for photography. Males are more visually distinctive than females and non-breeding birds, so if possible, time your visit to coincide with breeding season. Remember that this species dives frequently, so patience is essential—be ready to capture the moment when birds surface after underwater pursuits.