Species Profile
Brazilian Merganser
Mergus octosetaceus
Quick Facts
Conservation
CRCritically EndangeredLength
49–56 cm
Weight
700–1100 g
Wingspan
70–80 cm
Migration
Resident
Also known as: Pato-mergulhão
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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.
Identification & Characteristics
Colors
- Primary
- Brown
- Secondary
- Black
- Beak
- Black
- Legs
- Red
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
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.
Distribution
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.
Calls & Sounds
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
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
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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