Distribution

The Brazilian Merganser formerly was widespread in south central Brazil and in adjacent regions of Argentina and Paraguay (see Historical Changes). Currently the distribution is much more restricted.
A few recent sightings confirm this species still survives in Argentina and Paraguay (Giraudo and Povedano 2003). Although the situation of the species is extremely critical, some researchers believe that sizable overall populations may still exist in the extensive river systems of Misiones (Giraudo and Povedano 2003).
In recent decades, the species was reported from only a few localities in Brazil, most of them in protected areas and their surroundings, such as the Chapada dos Veadeiros National Park (Collar et al. 1992), Serra da Canastra National Park (Lamas 2006, Silveira and Bartmann 2001) and Jalapão State Park (Braz et al. 2003). Its occurrence was registered in the west of the state of Bahia (Pineschi and Yamashita 1999), although subsequent surveys failed to confirm the species in that region (Silveira 2008). One individual was recently observed for a few weeks in the Itacolomi State Park, in Minas Gerais State (De Paula et al. 2008) but it seems to be an occasional occurrence since no other individual was found in that region. Recent surveys also have failed to confirm its occurrence in the state of Paraná (Louri Klemann Júnior, pers. comm., 2007). In 2008, three individuals were observed in Patrocínio municipality, in the western part of the state of Minas Gerais, thus confirming its actual occurrence after 30 years of the first report in that locality (unpublished data). In summary, currently in Brazil, the Brazilian Merganser populations seem to be concentrated in a few localities in the states of Minas Gerais, Goiás and Tocantins.

Endemic to the Americas.

The species inhabits clean rivers and streams, with rapids and still waters, bordered by forests or native vegetation, and with an abundance of fish (Lamas 2006, Silveira and Bartmann 2001, Partridge 1956).  It is a shy bird and it is quite difficult to see in the wild (Silveira and Bartmann 2001, Collar et al. 1992, Bartmann 1988, Partridge 1956). It prefers sparsely populated areas and avoids human presence, although at some localities it is bolder and occurs closer to villages and small towns. The Brazilian Merganser seems to tolerate some environmental degradation if there are well preserved stretches in its territory so the birds can seek shelter (Lamas 2006).
Territory size of the Brazilian Merganser  varies between 5 -12 km of rivers and streams in the Serra da Canastra region (Silveira and Bartmann 2001).

The known original area of distribution of the Brazilian Merganser encompassed parts of Brazil, Argentina and Paraguay. In Brazil it included the mid-south, embracing the states of Goiás, Tocantins, Minas Gerais, São Paulo, Paraná and Santa Catarina (Collar et al. 1992). The reported occurrence mentioned for Mato Grosso do Sul (Collar et al. 1992) was based on anecdotal evidence and can not be confirmed (Luís Fábio Silveira, pers. comm., 2008). There is also an evidence of its historical occurrence in the Paraíba do Sul basin, in the state of Rio de Janeiro (Pacheco and Fonseca 1999).  Currently the distribution is much restricted, and the Brazilian Merganser largely is confined to a network of small populations (see The Americas).

No information.