Common Merganser

The Common Merganser (Mergus merganser) is a large, elegant diving duck native to the forested lakes and rivers of the Northern Hemisphere. Known as the 'Goosander' in Eurasia, this species is the largest of the three mergansers native to North America. It is highly adapted for aquatic life, possessing a long, streamlined body and a specialized, narrow bill with serrated edges designed to grasp slippery aquatic prey. During the breeding season, they are a striking sight on clean, fast-flowing rivers and deep lakes across North America, Europe, and Asia.

Identifying the Common Merganser is straightforward once you know key differences between sexes and similar species:

• Adult Male (Breeding): Features a brilliant white body, often tinged with a delicate peach or salmon-pink wash on the breast. The head is a deep, iridescent bottle-green that looks black in poor light, contrasting sharply with the white neck. The bill is long, thin, and bright red, lacking a prominent crest.
• Adult Female (and Immature): Features a sleek grey body and a rich, cinnamon-brown head with a shaggy crest pointing backward. A key field mark is the sharp, crisp boundary on the neck where the brown head ends and the white/grey chest begins, alongside a bright white chin patch.
• In Flight: They fly with a very straight, horizontal posture, resembling a long cylinder or pencil. Large white patches on the inner wings are highly visible on males.

Similar Species:

• Red-breasted Merganser: Males have a shaggy crest, a reddish-brown chest, and a dark grey body. Females are very similar to Common Mergansers, but the transition from the brown head to the pale throat/neck is fuzzy and blended, not sharply demarcated. Red-breasted Mergansers also prefer saltwater coastal environments, whereas Common Mergansers prefer freshwater.

Common Mergansers are primarily freshwater birds, setting them apart from the more salt-tolerant Red-breasted Merganser.

• Breeding Habitat: They favor clear, forested rivers, streams, and lakes with abundant fish populations. They require mature trees nearby for nesting cavities.
• Wintering Habitat: During the winter, they migrate south only as far as necessary to find open, unfrozen water. They can be found on large reservoirs, wide rivers, and occasionally brackish coastal estuaries when inland fresh waters freeze completely.
• Geographic Range: Their breeding range spans the boreal forests of North America, northern Europe, and northern Asia. They winter throughout southern Canada, the continental United States, central Europe, and East Asia.

The behavior of the Common Merganser is defined by its superb diving ability and aquatic hunting style.

• Feeding: Highly visual hunters, they swim along the surface with their heads submerged ('snorkeling') to scout for fish before diving. Their serrated bills allow them to grip trout, salmon, and other small fish firmly.
• Nesting and Breeding: Common Mergansers are cavity nesters, utilizing hollows in large mature trees (such as pileated woodpecker cavities), nest boxes, or occasionally rock crevices near water. The female lays 9-12 eggs. Shortly after hatching, the precocial ducklings jump down from the cavity—sometimes from heights of up to 100 feet—and follow their mother to the water. It is common to see a female swimming with multiple ducklings riding on her back.
• Vocalizations: Generally quiet. Females make a dry, harsh, repeated rasping 'karrr rrr' sound when alarmed or during flight. Males have a low, soft croak exhibited mainly during courtship.