Brazilian Merganser Bird Facts (Mergus octosetaceus)

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.

The Brazilian Merganser is not typically found in Woodland habitats.

The Brazilian Merganser is not typically found in Garden habitats.

The Brazilian Merganser can be found in Wetland habitats.

The Brazilian Merganser is not typically found in Coastal habitats.

The Brazilian Merganser is not typically found in Urban habitats.

The Brazilian Merganser is not typically found in Farmland habitats.

The Brazilian Merganser is not typically found in Grassland habitats.

The Brazilian Merganser is not typically found in Desert habitats.

The Brazilian Merganser is not typically found in Tundra habitats.

The Brazilian Merganser is not typically found in Rainforest habitats.

The Brazilian Merganser is not typically found in Mountain habitats.

The Brazilian Merganser is not typically found in Savanna habitats.

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.

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

Species that can be found in the area throughout the year

Argentina Brazil Paraguay

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Bird 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.

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.

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.

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.

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.

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.

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.

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

Main predators include large birds of prey, such as hawks and eagles, as well as medium-sized carnivorous mammals like otters and minks.

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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Visual Identification

Appearance

Size

Colours

Habitat and Distribution

Habitats

Distribution

Elevation Range

Climate zones

Distribution Map

Distribution by Region

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Behaviour and Ecology

Bird Attributes

Bird Attributes Explained

Attribute Categories:

Understanding the Ratings:

Agility

Strength

Adaptability

Aggressiveness

Endurance

Diet

Behaviour

Vocalisation

Nesting & Breeding

Conservation and Status

Global Conservation Status

Population Data

Rarity Index

Birdwatching Tips

Additional Information

Quick Facts

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Family:

Predators

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