Brazilian Merganser

• It is one of the six most threatened waterbirds in the world.
• It depends on pristine rivers: deforestation, mining, hydroelectric dams, pollution and even recreational canoeing degrade its habitat.
• Captive breeding began in 2011, when the Zooparque at Itatiba, in Brazil, raised the first ducklings; Prague Zoo joined in 2023 and had its first ducklings in 2025.

Skeleton type

Vertebrate - internal bony skeleton (bird)

Habitat and environment

Isolated stretches of clear, fast-flowing rivers in Brazil, Argentina and Paraguay. It nests in tree hollows or rock crevices near the banks. Each pair uses an average of 9 km of river, an enormous home range compared with other Mergus

Birth weight

Precocial: born covered in down and leaves the nest within a few hours

Size at birth

Precocial: born covered in down and leaves the nest within a few hours

Sexual maturity

2 years

Gestation / incubation

~33 days of incubation

Litter / clutch size

2 to 4 chicks per brood, averaging 2.7: lower than in other species of the genus

Sources consulted: IUCN Red List · Silveira y Bartmann 2002, Bird Conservation International (Serra da Canastra) · Eyton 1838 · Partridge (observaciones en Argentina, 1949-1954) · Vieillot 1817 · Threatened Waterfowl Specialist Group · Prague Zoo

Best time: All year round, though it is extremely elusive and hard to see

The pins mark the parks where its presence is documented.