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Brazilian merganser

Mergus octosetaceus

Braziliaanse zaagbek / Dunkelsäger / Harle du Brésil

Also read this article about the Brazilian Merganser Recovery Project.


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 (IUCN, 2013). 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.


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.


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 al2006, 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 al2006). The diet comprises fish, small eels, insect larvae, dobson flies (Corydalis spp.) and snails. In Serra da Canastra it eats mainly lambariAstyanax 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 (Ribeiroet 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).


Also read this article about the Brazilian Merganser Recovery Project.


More information: http://www.iucnredlist.org/details/22680482/0 



Above: adult Brazilian merganser at Zooparque Itatiba, Sao Paulo State, Brazil (captive breeding programme)



Above: adult Brazilian merganser (right) and juveniles at Zooparque Itatiba, Sao Paulo State, Brazil (captive breeding programme)



Above: stuffed merganser at Natural History Museum Naturalis, Leiden (NL)



Above: stuffed merganser at Natural History Museum Naturalis, Leiden (NL)



Above: stuffed merganser at Natural History Museum Naturalis, Leiden (NL)

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