Brazilian merganser -- 褐秋沙鸭 (Mergus octosetaceus)

Brazilian merganser on rock at edge of river
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Brazilian merganser fact file

Brazilian merganser description

GenusMergus (1)

The Brazilian merganser is one of the ten most threatened waterfowl in the world, with possibly fewer than 250 birds thought to remain (3). This dark, slender duck has a shiny dark-green hood with a long crest, which is usually shorter and worn-looking in females (4) (5). Upperparts are dark grey while the breast is light grey, getting paler towards the whitish belly, and a white wing patch (speculum) is particularly noticeable in flight (4) (5). The bill is long and dark (4), shorter in the female (2), and the legs are pink to orange-red (4) (5).

Size: 49 – 56 cm (2)

Brazilian merganser biology

Pairs occupy permanent territories of 8 to 14 km stretches of river (4), depending on the availability of suitable nesting and feeding sites (6). Nests are built in tree cavities and rock crevices (4). The breeding season is thought to last from June to August, but may vary geographically (4), and broods of between two and four chicks are usually raised (6).

The Brazilian merganser feeds mainly on fish, which it captures by diving in river rapids and backwater, but supplements this diet with molluscs and insects and their larvae (2) (3). These birds usually feed in pairs (2).


Brazilian merganser range

The Brazilian merganser exists in extremely low numbers at a few, highly disjunct localities in south-central Brazil. In 2002, the species was also found on the Arroyo Uruzú in Misiones, Argentina, the first record in the country for 10 years, despite extensive surveys. The bird was last recorded in Paraguay in 1984, where very little habitat remains, although local reports indicate that a few individuals may still survive there (4).


Brazilian merganser habitat

Inhabits shallow, fast-flowing streams and rivers with rapids and clear waters, surrounded by dense tropical forest (2) (4).


Brazilian merganser status

Classified as Critically Endangered (CR) on the IUCN Red List 2006 (1).

IUCN Red List species status – Critically Endangered


Brazilian merganser threats

The Brazilian merganser is extremely sensitive to habitat loss and degradation, and has suffered badly from pollution, siltation and disturbance of its rivers, which has resulted largely from deforestation, logging, agricultural expansion, cattle ranching, human habitation, hotel construction and, in the Serra da Canastra area, diamond-mining (3) (4) (7). Dam-building has also flooded suitable habitat, especially in Brazil and Paraguay (4), and intensifying ecotourism activities, such as rafting, may become another threat in the future (3). Other threats include inbreeding, hunting, competition, forest fires, egg-collecting, pesticides and predation (7). Fewer than 250 birds are thought to remain in the world, with the vast majority in Brazil. In Argentina, where very few individuals survive and extinction may be imminent, hunting and collection of exhibition specimens is believed to have contributed to the species’ decline (4).


Brazilian merganser conservation

This extremely rare bird occurs in three Brazilian national parks and, in Argentina, sections of the Arroyo Uruzú are also protected within the Uruguaí Provincial Park (4). Commercial diamond extraction was banned in the Serra da Canastra area in Brazil in 1996 (7). A Brazilian Merganser Recovery Team has been set up and a Brazilian Merganser action plan has been created, which details priority conservation projects (8) (9). In line with these plans, the Brazilian NGO Terra Brasilis has initiated a conservation program the world’s most important site, Serra da Canastra National Park in South Central Brazil (8) (9). The programme involves collecting basic information needed to adequately protect the species, such as studies of its breeding ecology and an inventory of its distribution within the Canastra range, as well as environmental education in both urban and rural areas (schoolchildren, teachers, farmers and other local people), and a campaign to market the species presence with the aim of ultimately making it a flagship species for the region (9). Nevertheless, even despite these efforts, there is a very real possibility of extinction in the wild becoming a reality and, without being established in captivity, this rare species would be lost to the world forever.

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

For more information on the Brazilian merganser see:



Information authenticated (02/05/07) by Dr Baz Hughes, Head of Species Conservation, Wildfowl and Wetlands Trust, Slimbridge, UK.



A bright and lustrous patch of colour found on the wings of ducks and some other birds.


  1. IUCN Red List (September, 2006)
  2. del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World – Ostrich to Ducks. Vol. 1. Lynx Edicions, Barcelona.
  3. Ducks Unlimited (October, 2006)
  4. BirdLife International (October, 2006)
  5. Arthur Grosset’s Birds (October, 2006)
  6. Silveira, L.F. and Bartmann, W.D. (2001) Natural history and conservation of Brazilian Merganser Mergus octosetaceus at Serra da Canastra National Park, Minas Gerais, Brazil. Bird Conservation International, 11: 287 - 300.
  7. Bruno, S.F. and Bartmann, W. (2003) Brazilian Mergansers in Serra da Canastra National Park, Minas Gerais State, Brazil. TWSG News, 14: 53 - 54.
  8. Hughes, B. (2003) Brazilian Merganser Workshop. TWSG News, 14: 10 - .
  9. Lins, L. (2003) Brazilian Merganser Study at Serra da Canastra. TWSG News, 14: 11 - .

Image credit

Brazilian merganser on rock at edge of river  
Brazilian merganser on rock at edge of river

© Charles Hesse

Charles Hesse


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