Species Profile
Red-breasted Merganser
Mergus serrator
Red-breasted Merganser
Quick Facts
Conservation
LCLeast ConcernAlso known as: Sawbill, Fish Duck, Sheldrakes
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Appearance
The Red-breasted Merganser is a striking diving duck with a slender, serrated bill. Males display a dark green head, a white neck ring, and a reddish-brown breast. Their sides are grey, with a white belly and black back.
Females are more subdued, with a reddish-brown head and grey body. Both sexes have a shaggy crest, but it's more pronounced in males during breeding season. Juveniles resemble females but with a shorter crest.
Identification & Characteristics
Male Colors
- Primary
- Red
- Secondary
- Black
- Beak
- Red
- Legs
- Orange
Female Colors
- Primary
- Brown
- Secondary
- White
- Beak
- Red
- Legs
- Orange
Female Markings
Shaggy crest and white chin
Attributes
Understanding Attributes
Rated 0–100 based on research and observation. A score of 50 is average across all bird species. These attributes are relative and don't necessarily indicate superiority.
Habitat & Distribution
Red-breasted Mergansers inhabit coastal marine waters, estuaries, and large freshwater lakes. They breed in northern regions of North America, Europe, and Asia, including parts of Scotland and Iceland.
During winter, they migrate to coastal areas in temperate zones. In the UK, they are common winter visitors along coastlines, with some breeding populations in northern Scotland.
Distribution
Where to See This Bird
Explore regional guides for locations where this bird has been recorded.
Scotland
Wales
Cumbria
Devon
Dorset
Essex
Hampshire
Isle of Wight
Kent
Merseyside
Northumberland
Norfolk
North Yorkshire
Stockton-on-Tees
West Sussex
Diet
Red-breasted Mergansers primarily feed on small fish, including herring, salmon, and trout. They also consume crustaceans, molluscs, and aquatic insects, including frogs and worms.
These birds swim with their heads lowered below the surface, watching for fish or other prey. Once sighted, they may dive down, kicking with their webbed feet and snapping at their prey with their toothy bill.
They often hunt cooperatively, herding fish into shallow water before diving to catch them with their serrated bills.
Behaviour
Red-breasted Mergansers are excellent swimmers and divers, often seen in small flocks on open water. They dive frequently to catch fish, staying submerged for up to 30 seconds.
During courtship, males perform elaborate head-pumping displays and short chases to attract females.
Calls & Sounds
Red-breasted Mergansers are generally quiet outside the breeding season. During courtship and nesting, they produce a variety of low, grunting calls.
Males emit a distinctive 'krrr-krrr' sound during displays, while females make a harsh, raspy 'gak-gak-gak' when alarmed or defending their brood.
Nesting & Breeding
Breeding occurs in late spring to early summer. Pairs form on wintering grounds or during migration, with elaborate courtship displays.
Females choose nest sites on the ground, often concealed by vegetation near water. They lay 6-12 (sometimes up to 25!) olive-buff eggs in a depression lined with down.
Incubation lasts about 29-35 days, performed solely by the female. Ducklings are precocial and can swim and dive shortly after hatching, fledging at 60-65 days.
Conservation
While currently listed as Least Concern, Red-breasted Mergansers face threats from oil spills, habitat degradation, and climate change.
Conservation efforts focus on protecting coastal wetlands and regulating pollutants in their aquatic habitats.
Birdwatching Tips
- Look for them on coastal waters, especially during winter
- Observe their distinctive diving behaviour and rapid wing beats in flight
- Listen for their harsh, grating calls during the breeding season
- In the UK, scan estuaries and sea lochs during autumn and winter months
Did You Know?
- Their serrated bill is specially adapted for gripping slippery fish.
- They can dive to depths of up to 30 feet (9 meters) when foraging.
- Red-breasted Mergansers are among the fastest flying ducks, reaching speeds of up to 80 mph (130 km/h).
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