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Brazilian Merganser Mergus octosetaceus
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Recent records from Brazil indicate that this species's status may be marginally better than previously thought. Nevertheless, the remaining known population is still extremely small and fragmented, and the perturbation, damming and pollution of rivers are likely to be causing continuing declines. For these reasons, it is listed as Critically Endangered. Further information on the population size (in particular whether it exceeds 250 mature individuals) and on the subpopulation structure may result in its downlisting to Endangered in the future.

Taxonomic source(s)
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.
SACC. 2006. A classification of the bird species of South America. Available at: #

49-56 cm. Dark, slender duck with long crest. Dark hood with petroleum-green sheen. Pale grey breast finely vermiculated dark, paler towards whitish belly. Dark grey upperparts. White wing speculum. Long, dark saw-bill. Pinky-lilac legs. Long, bushy hindcrest usually worn and shorter in females. Similar spp. Neotropic Cormorant Phalacrocorax brasilianus is larger and darker with hooked bill. Voice Harsh and dry jrrec contact call. Also louder nasal juac calls. Hints Hides under overhanging vegetation.

Distribution and population
Mergus octosetaceus occurs in extremely low numbers at a few highly disjunct localities in south-central Brazil. The species's stronghold is in and (mostly) around Serra da Canastra National Park, Minas Gerais (Lamas 2006), where recent surveys yielded a rough estimate of 70-100 territories, roughly equivalent to 140-200 mature individuals (L. V. Lins unpubl. data); if confirmed this would represent a significant increase to the size of the largest known subpopulation. Tributaries of the Rio São Francisco in west Bahia were thought to hold a significant population (Pineschi and Yamashita 1999), but a 2003 survey there failed to locate any birds. It has recently been found in Patrocínio municipality, Minas Gerais (I. Lamas in litt. 2012); a record from Itacolomi State Parque in the same state is though thought to refer to an accidental or escaped bird (Arvelino de Paula 2008, L. V. Lins in litt. 2012). In Goiás, there are records from Emas and Chapada dos Veadeiros national parks; the latter being surveyed in 2003-2004 with birds found just outside the park in the Rio das Pedras, and the total in the area thought to number fewer than 50 individuals (Disconzi 2012). In 1995, a small population was discovered on the Rio Tibagi, Paraná (Anjos et al. 1997), but searches in 1998 were unsuccessful (L. F. Silveira in litt. 1999). In 2002, another small population was discovered on the Rio Novo, in Jalapão State Park, Tocantins (Braz et al. 2003), and six expeditions in 2007 and 2008 surveying a c.55 km stretch of the Rio Novo located three breeding pairs (Barbosa and Almeida 2010), and four pairs along 115 km of river in 2010-2011 (IECOS Brasil 2013 per L. V. Lins in litt. 2013). It is believed extinct in Mato Grosso do Sul, Rio de Janeiro (Pacheco and Fonseca 1999), São Paulo, and Santa Catarina. In Misiones, Argentina, 12 individuals were found on the Arroyo Uruzú in 2002, the first records in the country for 10 years despite extensive surveys (Benstead 1994, Hearn 1994, J. C. Chebez in litt. 1999). In Paraguay, it was last recorded in 1984 and there is little (if any) habitat left. However, local reports indicate that a few individuals may still survive (R. P. Clay in litt. 2003).

Population justification
The population was estimated at 250 individuals in 1992, and was thought likely to have declined since given ongoing threats, however there are recent suggestions that the population may exceed this figure (L. V. Lins in litt. 2012). Recent estimates from the three main areas currently known to hold the species are of 70-100 territories (140-200 mature individuals) in the Serra da Canastra area (L. V. Lins in litt. 2012, 2013), fewer than 50 individuals at Chapada dos Veadeiros (Disconzi 2012) and eight at Jalapão (IECOS Brasil 2013 per L. V. Lins in litt. 2013), but these figures require confirmation and the population is currently precautionarily maintained within the band 50-249 mature individuals.

Trend justification
This species's population is suspected to have declined rapidly over the last 20 years (three generations), in line with habitat loss and degradation within its range, owing to the expansion of hydroelectric power schemes, soy bean cultivation and mining operations. It appears to have been extirpated from Paraguay.

It inhabits shallow, fast-flowing rivers, requiring rapids and clear waters. It occurs especially in the upper tributaries of watersheds but ranges into small rivers with patches of gallery forest surrounded by "cerrado" (tropical savanna) or within Atlantic Forest. It is non-migratory and does not abandon the stretch of river where it establishes its territory (Lamas 2006). Pairs have used 8-14 km stretches of river (Bartmann 1996, L. F. Silveira in litt. 1999), nesting in tree-cavities and rock-crevices (C. Yamashita in litt. 2000, Lamas and Santos 2004, Bruno et al. 2010). Breeding activity has been recorded between June and August (Lamas and Santos 2004, Bruno et al. 2006, Bruno et al. 2010), but timing may vary geographically. Incubation may last c.33 days (Bruno et al. 2010). Young birds have been observed between August and November (Lamas and Santos 2004, Bruno et al. 2006). The diet comprises fish, small eels, insect larvae, dobson flies (Corydalis spp.) and snails. In Serra da Canastra it eats mainly lambari Astyanax fasciatus. Territory size is believed to be related to the number of rapids, edgewaters, water speed, fish abundance and conservation of riparian vegetation (Lamas 2006). Its dispersal ability is unknown, but one young male banded in September 2010 was found breeding on another river 20 km away in June 2011 (Ribeiro et al. 2011).

Perturbation and pollution of rivers results largely from deforestation, agricultural expansion and, in the Serra da Canastra area, diamond-mining (Bartmann 1994, Bartmann 1996, M. Diniz in litt. 2013). Previously, the species was thought to rely on gallery forest which, although protected by law in Brazil, has been cleared illegally throughout much of the species's range. However, evidence suggests it will occur on unforested, undisturbed stretches of river through cerrado. All recent records of the species in the Serra da Canastra region refer to unprotected sites north of the National Park. These are sites under increasing pressure from mining, development of hydropower infrastructure and agriculture (L. V. Lins in litt. 2013). Mining has ceased in the immediate area of its known range but there is no additional habitat for dispersing birds (L. F. Silveira in litt. 1999), and it is thought that diamond mining will resume at Serra da Canastra in the near future (L. V. Lins in litt. 2012). Expanding agriculture and the construction of hydroelectric dams are considered the principal threats to the species (Braz et al. 2003). Dam-building has already caused severe declines across much of its range, and is increasing in scale (L. V. Lins in litt. 2012). Tourist activities result in river perturbation and have been recorded within known territories and inside national parks (Ibama 2006).

Conservation Actions Underway
The species is legally protected in all three range states. It occurs in three Brazilian national parks, two state parks and one private protected area (Braz et al. 2003), although there are no recent published records from Emas National Park. A species action plan has been published which outlines in detail its current status, ecology, threats and proposed conservation actions (Ibama 2006). In Argentina, sections of the Arroyo Uruzú are protected within the Uruguaí Provincial Park (P. Benstead verbally 2004). Regular monitoring of the population in Serra da Canastra National Park is conducted and in 2008 a team from the WWT and Terra Brasilis colour-ringed 14 individuals and fitted five of them with radio transmitters in order to increase knowledge of the species's movements and ecology (Braz et al. 2003, WWT 2008). Since then, 36 individuals have been banded, and the work has provided data on the species's sexual maturation and dispersal ability (Ribeiro et al. 2011). During one phase of a long-term study in Serra da Canastra National Park four pairs fledged 70 young in five years, representing a considerable contribution to the species's long-term survival and highlighting the importance of the park (Bruno et al. 2006). Nest boxes have recently been installed within the protected area (L. V. Lins in litt. 2012). Genetic studies are underway in the population, which will help to inform conservation decisions (Vilaça et al. 2011). A captive breeding programme was initiated in 2011 at the Poços de Caldas Breeding Center in Minas Gerais. Two young have been successfully reared so far (L. V. Lins in litt. 2012). An environmental education project began in 2004 and has been implemented at São Roque de Minas and Bonita.Conservation Actions Proposed
Assess the status of the Bahia population (L. F. Silveira in litt. 1999, L. V. Lins in litt. 2012). Continue to monitor the Serra da Canastra population. Develop and implement a fieldwork strategy using satellite images. Protect the watershed and riverine habitats of populations, especially in Bahia. Improve local awareness and promote riverbank protection. Conduct surveys in Paraguay to confirm local reports. Advocate for the expansion of the Chapada dos Veadeiros National Park in Brazil to include the population in the Rio das Pedras (Bianchi et al. 2005).  Continue to develop captive breeding programmes.

Related state of the world's birds case studies

Anjos, L. Dos; Schuchmann, K. L.; Berndt, R. 1997. Avifaunal composition, species richness, and status in the Tibagi river basin, Parana state, southern Brazil. Ornitologia Neotropical 8(1): 145-173.

Anon. 2009. Update from Brazil [Brazilian Merganser]. Waterlife: 12.

Barbosa, M. O.; Almeida, M. L. de. 2010. Novas observações e dados reprodutivos do pato-mergulhão Mergus octosetaceous na região do Jalapão, Tocantins, Brasil. Cotinga: 109-113.

Bartmann, W. 1994. The Brazilian Merganser (Mergus octocetaceus) - nearly extinct. Captive Breeding Specialist Group News 5(2): 7-8.

Bartmann, W. 1996. The Brazilian Merganser - nearly extinct? Threatened Waterfowl Research Group Newsletter: 32-34.

Benstead, P. 1994. Brazilian Merganser in Argentina: going, going. Cotinga: 8.

Bianchi, C. A.; Brant, S.; Brandao, R. A.; Brito, B. F. 2005. New records of Brazilian Merganser Mergus octosetaceous in the rio das Pedras, Chapada dos Veadeiros, Brazil. Cotinga 24: 72-74.

Bosso, A.; Gil, G. 2003. Pato serrucho: el ave más amenazada de la Argentina. Naturaleza & Conservacion: 8-15.

Braz, V. S.; Abreu, T. L. S.; Lopes, L. E.; Leite, L. O.; Franca, F. G. R.; Vasconcellos, M. M.; Balbino, S. F. 2003. Brazilian Merganser Mergus octosetaceus discovered in Jalapao State Park, Tocantins, Brazil. Cotinga 20: 68-71.

Bruno, S. F.; de Carvalho, R. B. A.; Bartmann, W. 2006. Reproductive rate and development of ducklings of Brazilian Merganser at Serra da Canastra National Park, Minas Gerais, Brazil, 2001-2005. TWSG News: 25-31.

Collar, N. J.; Butchart, S. H. M. 2013. Conservation breeding and avian diversity: chances and challenges. International Zoo Yearbook.

Collar, N. J.; Gonzaga, L. P.; Krabbe, N.; Madroño Nieto, A.; Naranjo, L. G.; Parker, T. A.; Wege, D. C. 1992. Threatened birds of the Americas: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, Cambridge, U.K.

Hearn, R. 1994. The current status of the Brazilian Merganser Mergus octosetaceus in Argentina. IWRB Threatened Waterfowl Research Group Newsletter: 14-15.

Hughes, B.; Dugger, B.; Cunha, H. J.; Lamas, I.; Goerck, J.; Lins, L.; Silveira, L. F.; Andrade, R.; Bruno, S. F.; Rigueira, S.; Barros, Y. de M. 2006. Action plan for the conservation of the Brazilian Merganser Mergus octosetaceus. IBAMA, Brasilia.

Lamas, I. R. 2006. Census of Brazilian Merganser Mergus octosetaceus in the region of Serra da Canastra National Park, Brazil, with discussion of its threats and conservation. Bird Conservation International 16: 145-154.

Lamas, I. R.; Santos, J. P. 2004. A Brazilian Merganser Mergus octosetaceus nest in a rock crevice, with reproductive notes. Cotinga 22: 38-41.

Pacheco, J. F.; Fonseca, P. S. M. Da. 1999. Evidência de ocorrência histórica do Pato-mergulhao Mergus octosataceus no Estado do Rio de Janeiro. Atualidades Ornitológicas 88: 10.

Paula, G. A. de; Cerqueira Júnior, M. C.; Ribon, R. 2008. Occurrence of the Brazilian Merganser (Mergus octosetaceous) in the southern border of the Espinaço Range, Minas Gerais, Brazil. Waterbirds 31(2): 289-293.

Pineschi, R. B.; Yamashita, C. 1999. Occurence, census and conservation of the Brazilian Merganser (Mergus octacetaceus) inside Brazil with notes about his feeding behavior and habitat preferences.

Ribeiro, F.; Lins, L. V.; Gomes, V. M.; Reis, E. S. 2011. Dispersão e maturidade sexual de Mergus octosetaceus Vieillot 1817 na região da Serra da Canastra, Minas Gerais, Brasil. Revista Brasileira de Ornitologia 19(3): 391-397.

Silveira, L. F. 1998. The birds of Serra da Canastra National Park and adjacent areas, Minas Gerais, Brazil. Cotinga 10: 55-65.

Vilaça, S. T.; Redondo, R. A. F.; Lins, L. V.; Santos, F. R. 2011. Remaining genetic diversity in Brazilian Merganser (Mergus octosetaceus). Conservation Genetics 13(1): 293-298.

WWT. 2008. Blog from Brazil: Rich Hearn blog - update from Brazil [Braziliian Mergansers]. Available at: #

Further web sources of information
Detailed species account from the Threatened birds of the Americas: the BirdLife International Red Data Book (BirdLife International 1992). Please note taxonomic treatment and IUCN Red List category may have changed since publication.

Detailed species account from the Threatened birds of the Americas: the BirdLife International Red Data Book (BirdLife International 1992). Please note, taxonomic treatment and IUCN Red List category may have changed since publication.

Explore HBW Alive for further information on this species

Recuento detallado de la especie tomado del libro Aves Amenazadas de las Americas, Libro Rojo de BirdLife International (BirdLife International 1992). Nota: la taxonomoía y la categoría de la Lista Roja de la UICN pudo haber cambiado desde esta publicación.

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Benstead, P., Bird, J., Butchart, S., Calvert, R., Capper, D., Clay, R., Mazar Barnett, J., Pilgrim, J., Sharpe, C J, Symes, A., Taylor, J. & Khwaja, N.

Bosso, A., Chebez, J., Clay, R., Gil, G., Silveira, L., Yamashita, C., Lamas, I., Lins, L., Cockle, K., Disconzi, G. & Diniz, M.

Recommended citation
BirdLife International (2014) Species factsheet: Mergus octosetaceus. Downloaded from on 30/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from on 30/08/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Brazilian merganser (Mergus octosetaceus) 0

Key facts
Current IUCN Red List category Critically Endangered
Family Anatidae (Ducks, Geese, Swans)
Species name author Vieillot, 1817
Population size 50-249 mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 51,300 km2
Country endemic? No
Links to further information
- Additional Information on this species