Mergus octosetaceus

Taxonomy

Assessment Information

Geographic Range

Population

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	ANSERIFORMES	ANATIDAE

Scientific Name:

Mergus octosetaceus

Species Authority:

Vieillot, 1817

Common Name/s:

English

–

Brazilian Merganser

Taxonomic Notes:

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered C2a(i) ver 3.1

Year Published:

2012

Assessor/s:

BirdLife International

Reviewer/s:

Butchart, S. & Symes, A.

Contributor/s:

Bosso, A., Chebez, J., Clay, R., Gil, G., Lamas, I., Lins, L., Silveira, L. & Yamashita, C.

Justification:
Recent records from Brazil, and particularly a recent northerly range extension, indicate that this species's status is better than previously thought. Nevertheless, the remaining population is still extremely small and severely fragmented, and the perturbation, damming and pollution of rivers continue to cause declines. For these reasons, it is listed as Critically Endangered. If recent suggestions that the population exceeds 250 mature individuals can be confirmed, the species will be eligible for downlisting to Endangered.

History:

2010	–	Critically Endangered
2009	–	Critically Endangered
2008	–	Critically Endangered
2006	–	Critically Endangered
2004	–	Critically Endangered
2000	–	Critically Endangered
1996	–	Critically Endangered
1994	–	Critically Endangered

Geographic Range [top]

Range Description:	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 65-100 territories, roughly equivalent to 130-200 individuals (L. V. Lins unpubl. data); if confirmed this would represent a significant increase to the size of the largest known subpopulation. A recently discovered population on tributaries of the Rio São Francisco in west Bahia was thought to hold a significant population (Pineschi and Yamashita 1999), but a 2003 survey there failed to locate any birds (BirdLife International Brazil Programme unpubl. data). 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. 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). 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).
Countries:	Native: Argentina; Brazil; Paraguay
Range Map:	Click here to open the map viewer and explore range.

Population [top]

Population:	The population was estimated at 250 individuals in 1992. Although no complete census has been conducted since this estimate, threats have continued, hence the current population is likely to be lower than this figure, thus the population is placed in the band 50-249 mature individuals. There are recent suggestions that the population may exceed this figure (L. V. Lins in litt. 2012), but this requires confirmation.
Population Trend:	Decreasing

Population:

The population was estimated at 250 individuals in 1992. Although no complete census has been conducted since this estimate, threats have continued, hence the current population is likely to be lower than this figure, thus the population is placed in the band 50-249 mature individuals. There are recent suggestions that the population may exceed this figure (L. V. Lins in litt. 2012), but this requires confirmation.

Population Trend:

Decreasing

Habitat and Ecology [top]

Habitat and Ecology:	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).
Systems:	Freshwater

Habitat and Ecology:

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).

Systems:

Freshwater

Threats [top]

Major Threat(s):	Perturbation and pollution of rivers results largely from deforestation, agricultural expansion and, in the Serra da Canastra area, diamond-mining (Bartmann 1994, Bartmann 1996). 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. 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).

Major Threat(s):

Perturbation and pollution of rivers results largely from deforestation, agricultural expansion and, in the Serra da Canastra area, diamond-mining (Bartmann 1994, Bartmann 1996). 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. 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 [top]

Conservation Actions:	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). The WWT continues to raise funds for this species, and over the next 12 months hopes to continue monitoring and ecological research and develop education work to address the threats faced by the species (Anon. 2009). 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). 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 newly discovered population in the Rio das Pedras (Bianchi et al. 2005).

Conservation Actions:

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). The WWT continues to raise funds for this species, and over the next 12 months hopes to continue monitoring and ecological research and develop education work to address the threats faced by the species (Anon. 2009). 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).

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 newly discovered population in the Rio das Pedras (Bianchi et al. 2005).

Citation:	BirdLife International 2012. Mergus octosetaceus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. <www.iucnredlist.org>. Downloaded on 22 May 2013.
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