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Mergus serrator - Red-breasted Merganser

Red-breasted Merganser image

Geographic range:

Holarctic, much of North America

Key features:

Long bodied diving duck, wispy, rust colored trailing shaggy crest

Similar species:

Mergus merganser -- Common Merganser


bay (sandy shore), estuary, protected sandy beaches

Primary common name:

Red-breasted Merganser

General grouping:

Seabirds and shorebirds

ITIS code:


Geographic Range

Range Description:

The Red-breasted Merganser has a wide distribution in the Northern Hemisphere, breeding up to 75°N. It winters chiefly along coasts from Alaska south to California, from Maritime Provinces south to Florida, and along the Gulf Coast. It is largely found at sea, inhabiting deeper offshore waters as well as inshore areas. It is also found in Eurasia. The breeding range of the red-breasted merganser generally extends farther north and not as far south as the common merganser. The principal region of overlap is in southeastern and southern Canada. Although red-breasted mergansers breed over most of Alaska, including the Aleutian Islands, they are most abundant on areas adjacent to the Bering Sea. They nest east through the tundra of Labrador and northern Quebec to central Baffin Island. They also are the only nesters on the tundra along the south and west coasts of Hudson Bay, north to Eskimo Point and Coronation Gulf, then south through the tundra and most of the open boreal forests of the Northwest and Yukon territories.


bay (sandy shore), estuary, protected sandy beaches

Habitat notes:

Breeds on wooded lakes and tundra ponds; winters mainly on salt water.


Relative abundance:

The Red-breasted Merganser is fairly common along the coast in MBNMS, but rare in the summer.

Species Description

General description:

A large, thin, diving duck with a long thin bill, the Red-breasted Merganser is found in large lakes, rivers and the ocean. An expert diver, it usually runs across the water to become airborne and can fly low and noiselessly over water at considerable speed. Its serrated mandibles help in capturing underwater prey. It is similar in distribution and ecology to the Common Merganser but, in contrast, it occurs more frequently in salt water and estuaries, typically nests on the ground, and has dark-colored down. In breeding plumage the male’s head is iridescent greenish black with a trailing wispy, double crest and a white neck ring. Its chest is deep rust speckled with black. Its back is dark with a long white patch on the black wings. The tail is gray, the bill bright scarlet-orange, long (2 in), pointed with serrated, tooth-like edges. Legs are orange, and eyes red. In nonbreeding plumage the head is rust brown with a ragged double crest. The chin, breast, back, wings and tail are gray. Belly and flanks are white. In this plumage it is much like the female, except there is less white on chin, a darker back, and wings with larger white patches. The female’s plumage is the same year round: head rusty brown with long, ragged, double crest, whitish chin and throat, with neck, breast, back, wings and tail gray. Belly and flanks white. Bill a dull scarlet-orange. White patch in wing visible in flight. Immature resembles adult female. Except for their smaller size, female red-breasted mergansers greatly resemble common mergansers. The two species can be distinguished by noting that the white throat of the red-breasted merganser merges imperceptibly with the brown head, whereas the common merganser's throat is more sharply defined against its reddish-brown head. They are usually silent; with various croaking and grunting notes during courtship.

Distinctive features:

Largish, thin, diving duck,male's head, iridescent green in breeding season, rust in nonbreeding season with trailing shaggy double crest, reddish breast


(females smaller than males) Length: 20.1-25.2 in (51-64 cm) Wingspan: 26-29.1 in (66-74 cm) Weight: 28.2-47.6 oz (800-1350 g)

Natural History

General natural history:

The Red-breasted Merganser breeds farther north and winters farther south than the other American mergansers. They return to the breeding grounds from April to June when groups of males begin unusual courtship behaviors to attract a mate. They swim in synchrony tucking their head into the shoulders, raising the crest, and pointing the bill slightly upwards. The head is shaken from side to side in a rapid flicking motion. Then the head and neck are quickly raised and lowered towards the water with the crest erect. After pairing the female will search for a nest site, often among groups of other ducks, gulls or terns. A simple nest is scratched into the bare ground in a concealed location or in a natural cavity or burrow, typically within 25 m from water. Gradually the female lines the nest with feathers and vegetation. Usually 8 to 10 eggs are laid and incubated for 31 to 32 days by the female. During this time, the male leaves the breeding site and travels along the coast in small groups to molt. The chicks fledge after 60 to 65. They reach maturity at 2 years of age.


Adult red-breasted mergansers are hunted by humans, owls and red foxes. Minks, gulls, and ravens prey upon eggs and young.


The Red-breasted Merganser feeds on small fish, (herring, fry, minnows) including juvenile fish in nurseries and salmon streams. It will also eat fish eggs and occasionally shrimp, crabs, and aquatic invertebrates, such as crustaceans and insects (especially the young), as well as some plant material.

Feeding behavior


Feeding behavior notes:

Red-breasted mergansers may forage alone or in groups, with individuals cooperating to work schools of fish into shallow water, hunting on lakes, rivers, coastal bays and at sea.. They typically swim along the water’s surface, repeatedly submerging their head to scan for prey. Diving to depths of up to five m, the red-breasted merganser catches its prey after an underwater pursuit, or by probing at rocky crevices with its elongated, serrated bill.

April - May

May - September


The red-breasted merganser breeds along the wooded shorelines of deep lakes, rivers and streams, as well as shallow bays and estuaries with sandy bottoms, preferring narrow channels with small rocky islands and grassy banks rather than large, open expanses of water. They are often observed at river mouths where, on islands, they breed in loose colonies and in association with terns and gulls. They are seasonally monogamous, but there is good evidence that extra-pair copulations may be frequent. Males perform a courtship display and call to attract females. Usually several males display around a single female in an attempt to win her favor. Males hold their heads close to their body with the crest raised and their bill pointing up, they then do 1 of 2 alternate displays: the "head shake" and the "salute curtsy." The head shake involves flicking the head from side to side. In the salute curtsy the male drops the bill forward, then rapidly flicks it up while straightening his neck and raising the chest above the water, the chest is then dropped back into the water, this may also be accompanied by kicking. A "yeow" call is used during the salute portion of the curtsy salute display. Females use a display that incites male courtship behavior, making a bobbing motion through the water as she holds her bill downwards. Females first breed at the age of two years. Pairs generally form in late winter and during spring migration, although some evidence of pairing may be evident in the late fall. Breeding is late in the season, and often the young do not fledge until September. The nest is located in a sheltered spot on the ground, usually near water. They have been found nesting in marshes, on rocky islets, on vegetated islands in large lakes, in bank recesses and under abush or piles of driftwood. The nest is a simple depression lined with vegetation and down. The female lays 8 to 10 olive-buff eggs (2.5 in), and sometimes lays them in the nests of other females. Males usually leave when incubation begins. Incubation is by the female alone and lasts for 28 to 35 days. Within a day or so of hatching, the young follow the female to water where they feed themselves. Often, in areas of high-density nesting, two or more broods will join and form a crèche, with one or more females tending them. Within a few weeks, the females typically abandon the young, who cannot fly until they are about two months old.

September - April

September - October


The bulk of the red-breasted merganser populations that breed in the interior of North America migrate toward the Atlantic or Pacific coasts before reaching their wintering grounds, though a small number migrate into the Great Lakes. Some remain there for winter, but many continue farther south to wintering grounds along the Gulf Coast and probably along the mid-Atlantic coast. A few thousand have been known to fly south from central Canada across the Great Plains to winter along the Texas coast. Red-breasted mergansers typically migrate in small flocks of 5 to 15, with coastal flights occurring during the day and inland flights at night.

Monterey Bay National Marine Sanctuary:

Classified as Least Concern (LC) on the IUCN Red List
Click on an image below to view a larger version in the SIMoN Photo Library. You will also be able to view important information on each photo such as photographer, date, caption and more.
Ehrlich, P., D.S. Dobkin, and D. Wheye. 1988. The Birders Handbook: A Field Guide to the Natural History of North American Birds. Simon & Schuster Inc., New York. 785 p.
NOAA. 1994. Beached marine birds and mammals of the North American West Coast: a revised guide to their identification. NOAA Sanctuaries and Reserves Division, U.S. Department of Commerce
Roberson, D. 2002. Monterey Birds 2nd edition. Monterey Peninsula Audubon Society, Carmel, CA. 536 p.
Sibley, D.A. 2000. The Sibley Guide to Bird. Alfred A. Knopf, Inc. 545 p.
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Audubon Society.

Birds of North America Online


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Cornell Lab of Ornithology
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