• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
C2a(i)	C2a(i); D	C2a(i); D1

Red List history

Year	Category	Criteria
2019	Critically Endangered	C2a(i)
2016	Critically Endangered	C2a(i)
2015	Critically Endangered	C2a(i)
2013	Critically Endangered	C2a(i)
2012	Critically Endangered	C2a(i)
2010	Critically Endangered	C2a(i)
2009	Critically Endangered	C2a(i)
2008	Critically Endangered
2006	Critically Endangered
2004	Critically Endangered
2000	Critically Endangered
1996	Critically Endangered
1994	Critically Endangered
1988	Threatened

Migratory status	not a migrant	Forest dependency	does not normally occur in forest
Land-mass type	continent	Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,380,000 km2	medium
Number of locations	8	-
Severely fragmented?	yes	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	50-249 mature individuals	medium	estimated	1994
Population trend	decreasing	poor	inferred	2000-2010
Generation length	6.5 years	-	-	-
Number of subpopulations	6	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

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, Barbosa et al. 2015), but these figures require confirmation. 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.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Argentina	extant	native	yes
Brazil	extant	native	yes
Paraguay	extant	native	yes

Country/Territory	IBA Name
Argentina	Cuenca del Piray Miní
Argentina	Parque Provincial Urugua-í
Brazil	Jalapão
Brazil	Parque Nacional da Chapada dos Veadeiros e Adjacências
Brazil	Rio Arrojado
Brazil	Serra da Canastra

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Wetlands (inland)	Permanent Rivers/Streams/Creeks (includes waterfalls)	major	resident
Altitude	0 - 1100 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Agro-industry farming	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Species mortality
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation
Energy production & mining	Mining & quarrying	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Rapid Declines		Medium Impact: 6
		Stresses Species disturbance
Natural system modifications	Dams & water management/use - Dams (size unknown)	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Pollution	Agricultural & forestry effluents - Type Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation

Purpose	Scale
Sport hunting/specimen collecting	subsistence, national

---

Recommended citation
BirdLife International (2024) Species factsheet: Brazilian Merganser Mergus octosetaceus. Downloaded from https://datazone.birdlife.org/species/factsheet/brazilian-merganser-mergus-octosetaceus on 18/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 18/12/2024.