Red-breasted Merganser
Mergus serrator
Visual Identification
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.
Size
Length
52cm to 58cm
Wingspan
70cm to 86cm
Weight
800g to 1.35kg
Habitat and Distribution
Habitats
Woodland
Garden
Wetland
Coastal
Urban
Farmland
Grassland
Desert
Tundra
Rainforest
Mountain
Savanna
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.
Elevation Range
Sea level to 1,500 meters
Climate zones
Temperate, Subarctic
Distribution Map
This map gives you a rough idea of where you might spot a Red-breasted Merganser. The coloured areas show countries where these birds have been seen.
A few things to keep in mind:
- Birds might not be everywhere in the coloured areas, for example, they may be present around the coast of that country
- Where birds live can change with seasons and available food
- This map is quite simple - it doesn't show exact locations
We're working on making our maps even better! Soon, we hope to show you:
- More detailed maps for bigger countries, including state and region
- How birds move around during different seasons
Distribution by Region
Behaviour and Ecology
Bird Attributes
This feature is in beta. We'd love your feedback to improve it!
Share your thoughtsBird Attributes Explained
Our bird attributes system rates various aspects of a bird's capabilities on a scale of 0-100, based on data from field observations, scientific studies, and expert knowledge.
Attribute Categories:
- Agility: Manoeuvrability, speed, and grace in flight or movement.
- Strength: Physical power, often correlating with size and hunting abilities.
- Adaptability: Ability to thrive in various environments or changing conditions.
- Aggressiveness: Territorial behaviour and assertiveness, particularly during breeding seasons.
- Endurance: Stamina, often seen in migration patterns or foraging behaviours.
Understanding the Ratings:
- 0-20: Very Low
- 21-40: Low
- 41-60: Average
- 61-80: High
- 81-100: Very High
Remember, these attributes are relative to other bird species and don't necessarily indicate superiority.
Hover over the icon next to each attribute for more information.
Tap the icon next to each attribute for more information.
Agility
Reflects the bird's manoeuvrability, speed, and grace in flight or movement.
The Red-breasted Merganser demonstrates remarkable agility, particularly in aquatic environments. Their ability to dive to depths of 9 metres, stay submerged for up to 30 seconds, and execute rapid wing beats in flight showcases their exceptional manoeuvrability.
Strength
Indicates the bird's physical power, often correlating with size and hunting abilities.
While not the strongest of waterfowl, Red-breasted Mergansers possess adequate strength for their size and lifestyle. Their ability to catch and hold slippery fish with their serrated bills, coupled with their capacity for long-distance migration, indicates a respectable level of strength.
Adaptability
Represents the bird's ability to thrive in various environments or changing conditions.
These birds exhibit high adaptability, thriving in various aquatic habitats from sea level to 1,500 metres elevation. Their ability to inhabit both marine and freshwater environments, coupled with their successful migration patterns, demonstrates significant adaptability to changing conditions.
Aggressiveness
Measures the bird's territorial behaviour and assertiveness, particularly during breeding seasons.
Red-breasted Mergansers display moderate aggressiveness. While generally not overly confrontational, females produce harsh, raspy calls when alarmed or defending their brood. Their cooperative hunting behaviour suggests a level of assertiveness in foraging activities.
Endurance
Reflects the bird's stamina, often seen in migration patterns or foraging behaviours.
The endurance of Red-breasted Mergansers is noteworthy. Their long-distance migration capabilities, combined with their ability to dive frequently and fly at speeds up to 130 km/h, indicate substantial endurance. However, their relatively short lifespan of 9-12 years suggests some limitations in long-term stamina.
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.
Vocalisation
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 and Status
Global Conservation Status
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
Additional Information
Quick Facts
Predators
Main predators include large gulls, ravens, foxes, and minks. Eggs and ducklings are particularly vulnerable to predation.
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).
Similar Birds
References
- 1
website: BirdLife International. 2018. Mergus serrator. The IUCN Red List of Threatened Species 2018: e.T22680485A132053220.
View source - 2 3
report, 2016: Wetlands International
- 4
website, 2010: Fransson et al., EURING list of longevity records for European birds
View source
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