Brazilian Merganser
Critically EndangeredMergus octosetaceus
Visual Identification
Appearance
The Brazilian Merganser is a medium-sized duck with a distinctive long, thin, serrated black bill. Its head and upper neck are dark green with a long, shaggy crest. The body is predominantly dark brown above and pale grey below, with darker striping that fades towards the belly.
Males have a more prominent crest and a larger white wing patch than females. Juveniles resemble females but have a duller plumage and a less developed crest.
Size
Length
49cm to 56cm
Wingspan
70cm to 80cm
Weight
700g to 1.1kg
Colours
Males and females have similar plumage
Primary Colour
Brown White Green
Secondary Colour
Black Grey
Beak Colour
Black
Leg Colour
Red Grey
Habitat and Distribution
Habitats
Woodland
Garden
Wetland
Coastal
Urban
Farmland
Grassland
Desert
Tundra
Rainforest
Mountain
Savanna
Distribution
Brazilian Mergansers inhabit clear, fast-flowing rivers and streams in central-southern Brazil, eastern Paraguay, and northeastern Argentina. They prefer waterways with rocky bottoms and forested banks in areas of high elevation.
Due to habitat loss, their distribution is highly fragmented. They are non-migratory, maintaining year-round territories along suitable waterways within their limited range.
Elevation Range
Up to 1,000 meters
Climate zones
Tropical, Subtropical
Distribution Map
This map gives you a rough idea of where you might spot a Brazilian 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
Behaviour and Ecology
Bird Attributes
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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.
Exceptional agility demonstrated through precise diving capabilities in fast-flowing rivers, swift underwater manoeuvring to catch fish, and ability to navigate rocky waterways. Their specialised swimming and diving abilities make them particularly nimble in aquatic environments.
Strength
Indicates the bird's physical power, often correlating with size and hunting abilities.
Moderate strength evidenced by their ability to swim against strong currents and catch fish underwater. Their medium size (700-1100g) and wingspan (70-80cm) suggest reasonable muscular capability, though not exceptional compared to larger waterfowl.
Adaptability
Represents the bird's ability to thrive in various environments or changing conditions.
Limited adaptability reflected in their specific habitat requirements for clear, fast-flowing rivers with rocky bottoms and forested banks. Their critically endangered status and inability to adjust to habitat alterations suggests poor adaptation to environmental changes.
Aggressiveness
Measures the bird's territorial behaviour and assertiveness, particularly during breeding seasons.
Generally shy and non-aggressive birds that prefer to flee rather than confront threats. While they defend their territory during breeding season, they're notably wary of disturbances and typically avoid confrontation.
Endurance
Reflects the bird's stamina, often seen in migration patterns or foraging behaviours.
Strong endurance demonstrated by their ability to dive for up to 30 seconds whilst foraging, swim continuously in fast-flowing waters, and maintain year-round territories. Their specialised lifestyle requires sustained physical activity throughout the day.
Diet
Brazilian Mergansers primarily feed on small fish, which they catch by diving and pursuing underwater. They also consume aquatic insects, crustaceans, and molluscs.
Their serrated bills are specially adapted for gripping slippery prey in fast-flowing water.
Behaviour
Brazilian Mergansers are excellent swimmers and divers, using their specialised bills to catch fish underwater. They are typically seen in pairs or small family groups, maintaining strong pair bonds throughout the year. These birds are shy and wary, often fleeing at the first sign of disturbance.
Vocalisation
Brazilian Mergansers are generally quiet birds. Their vocalisations include soft, low whistles and quiet grunts.
During courtship, males produce a series of low, nasal 'rreck-rreck' calls. Alarm calls consist of sharp, high-pitched whistles, often given when disturbed.
Nesting & Breeding
Brazilian Mergansers form monogamous pairs and breed during the dry season, typically from June to August. They nest in natural cavities in trees or rocky crevices near water, often reusing the same site year after year.
The female lays 2-6 cream-coloured eggs in a nest lined with down. Incubation lasts about 32 days, performed solely by the female while the male guards the territory.
After hatching, both parents care for the ducklings, which can swim and dive shortly after birth. The young remain with their parents for several months, learning essential survival skills.
Conservation and Status
Global Conservation Status
The Brazilian Merganser is critically endangered due to habitat loss, water pollution, and dam construction.
Conservation efforts focus on protecting remaining habitats, reducing water pollution, and implementing captive breeding programs to boost wild populations.
Birdwatching Tips
- Look for them along fast-flowing, clear rivers with rocky bottoms
- Observe early morning or late afternoon when they are most active
- Listen for their soft, low whistling calls
- Be patient and quiet, as they are easily startled
Additional Information
Quick Facts
Other names:
Pato-mergulhão
Family:
AnatidaePredators
Main predators include large birds of prey, such as hawks and eagles, as well as medium-sized carnivorous mammals like otters and minks.
Did You Know?
- Brazilian Mergansers are one of the rarest waterfowl species in the world.
- They have special nictitating membranes that act like goggles underwater.
- These birds can dive up to 30 seconds at a time while foraging.
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References
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website: BirdLife International. 2019. Mergus octosetaceus. The IUCN Red List of Threatened Species 2019: e.T22680482A143756439.
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