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

Assessment Information [top]

Red List Category & Criteria:

Critically Endangered C2a(i) ver 3.1

Year Published:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Calvert, R., Symes, A., Butchart, S.

Contributor/s:

Clay, R., Yamashita, C., Bosso, A., Chebez, J., Silveira, L., Gil, G.

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.

History:

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 strongholds are a recently discovered population on tributaries of the rio São Francisco in west Bahia⁸, and in and (mostly) around Serra da Canastra National Park, Minas Gerais, where a total of 81 individuals was estimated after surveys in 2001-2002²⁰. It was recently found in Itacolomi State Parque, Ouro Prêto Municipality, Minas Gerais¹⁶. 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 Pedras¹⁸. Outside of Bahia and Serra da Canastra National Park, this now represents one of the largest remaining populations¹⁸. In 1995, a small population was discovered on the rio Tibagi, Paraná¹, but searches in 1998 were unsuccessful¹⁰. In 2002, another small population was discovered on the rio Novo, in JalapãoState Park, Tocantins¹³, and six expeditions in 2007 and 2008 surveying a c.55-km stretch of the rio Novo located three breeding pairs²⁴. It is believed extinct in Mato Grosso do Sul, Rio de Janeiro⁷, São Paulo, and Santa Catarina. In Misiones, Argentina, the species was found on the Arroyo Uruzú12 in 2002, the first records in the country for 10 years despite extensive surveys^4,5,6. 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 survive¹⁴. The global population is likely to be lower than the 250 birds estimated in 1992².
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 (Bartmann 1994). 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.
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 or within Atlantic Forest. It is non-migratory and does not abandon the stretch of river where it establishes its territory²⁰. Pairs have used 8-14 km stretches of river^3,10, nesting in tree-cavities and rock-crevices^11,17,25. Breeding activity has been recorded in June-August^17,19,25, but timing may vary geographically. Incubation may last c.33 days²⁵. Young birds have been observed in August-November^17,19. The diet comprises fish, small eels, insect larvae, dobson flies (Corydalis sp.) 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 vegetation²⁰.
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 or within Atlantic Forest. It is non-migratory and does not abandon the stretch of river where it establishes its territory²⁰. Pairs have used 8-14 km stretches of river^3,10, nesting in tree-cavities and rock-crevices^11,17,25. Breeding activity has been recorded in June-August^17,19,25, but timing may vary geographically. Incubation may last c.33 days²⁵. Young birds have been observed in August-November^17,19. The diet comprises fish, small eels, insect larvae, dobson flies (Corydalis sp.) 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 vegetation²⁰.

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^2,3. 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 birds¹⁰. Expanding agriculture and the construction of hydroelectric dams are considered the principal threats to the species¹³. Dam-building has already caused severe declines across much of its range. Tourist activities result in river perturbation and have been recorded within known territories and inside national parks²¹.

Major Threat(s):

Perturbation and pollution of rivers results largely from deforestation, agricultural expansion and, in the Serra da Canastra area, diamond-mining^2,3. 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 birds¹⁰. Expanding agriculture and the construction of hydroelectric dams are considered the principal threats to the species¹³. Dam-building has already caused severe declines across much of its range. Tourist activities result in river perturbation and have been recorded within known territories and inside national parks²¹.

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 Reserva Particular do Patrimônio Natural (RPPN)¹³, 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 actions²¹. In Argentina, sections of the Arroyo Uruzú are protected within the Uruguaí Provincial Park¹⁵. 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 in the park and fitted five of them with radio transmitters in order to increase knowledge of the species's movements and ecology^13,22. 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 park¹⁹. A Brazilian Merganser Recovery Team has been established with the aim of developing an action plan for its recovery¹⁸. There is a proposal to extend the boundaries of Chapada dos Veadeiros National Park to incorporate the newly discovered population in the rio das Pedras¹⁸. The WWT continues to raise funds for this species, and over the next 12 months hopes to continue monitoring and ecological research, develop education work to address the threats faced by the species and carry out a feasibility study for the development of a captive population²³. Conservation Actions Proposed Assess the status of the Tibagi, Arroyo Uruzú and Novo populations¹⁰. 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. Install nest-boxes for populations outside Serra da Canastra National Park. 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 Pedras¹⁸. Consider captive breeding.

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 Reserva Particular do Patrimônio Natural (RPPN)¹³, 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 actions²¹. In Argentina, sections of the Arroyo Uruzú are protected within the Uruguaí Provincial Park¹⁵. 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 in the park and fitted five of them with radio transmitters in order to increase knowledge of the species's movements and ecology^13,22. 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 park¹⁹. A Brazilian Merganser Recovery Team has been established with the aim of developing an action plan for its recovery¹⁸. There is a proposal to extend the boundaries of Chapada dos Veadeiros National Park to incorporate the newly discovered population in the rio das Pedras¹⁸. The WWT continues to raise funds for this species, and over the next 12 months hopes to continue monitoring and ecological research, develop education work to address the threats faced by the species and carry out a feasibility study for the development of a captive population²³.

Conservation Actions Proposed
Assess the status of the Tibagi, Arroyo Uruzú and Novo populations¹⁰. 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. Install nest-boxes for populations outside Serra da Canastra National Park. 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 Pedras¹⁸. Consider captive breeding.

Citation:	BirdLife International 2010. Mergus octosetaceus. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 17 May 2012.
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