Horned Curassow

The horned curassow (''Pauxi unicornis''), or southern helmeted curassow, is a species of bird in the family Cracidae found in humid tropical and subtropical forests. It was first described by James Bond and Rodolphe Meyer de Schauensee in 1939 from a specimen collected in Bolivia, and further birds that were described from Peru in 1971 were thought to be a new subspecies. However, the taxonomical position (as subspecies or independent species) of the birds found in Peru in 1971 is unclear. The horned curassow as originally described is endemic to Bolivia. It is a large, predominantly black bird with a distinctive casque on its forehead. It is an uncommon bird with a limited range and is suffering from habitat loss, and the International Union for Conservation of Nature has rated its conservation status as being " critically endangered".

Taxonomy and systematics

In 1937 while in Bolivia Mr M. A. Carriker found two birds, a male and female, which were in the cracid family. The specimens were subsequently described as a new species by James Bond and Rodolphe Meyer de Schauensee in 1939 and given the scientific name ''Pauxi unicornis'' placing it in a genus ''Pauxi'' alongside the species ''P. pauxi''. In 1969 another two birds, again a male and female were discovered which resembled those found by Mr. Carriker in 1937. However this time they were found in Peru a long way from the previous ''P. unicornis'' discoveries in Bolivia. These Peruvian specimens were described by John Weske and John Terborgh in 1971 as a new subspecies of ''P. unicornis'' which they named in honour of Maria Koepcke.

Although the consensus at the time of discovery for ''P. unicornis'' to be a species with two subspecies in the genus ''Pauxi'', many different suggestions have been made since. Some suggestions relate to the grouping of species and subspecies within the genus ''Pauxi''. In 1943 Wetmore and Phelps described a new subspecies of the closely related ''P. pauxi'' called ''P. p. gilliardi''. When Wetmore and Phelps looked at the three ''Pauxi'' forms known at the time, they concluded that ''P. p. gilliardi'' was an intermediate form between ''P. pauxi'' and ''P. unicornis''. As a result of this they grouped all three forms into a single species with ''unicornis'' becoming a subspecies of ''pauxi''. This position was subsequently rejected by Charles Vaurie who argued that ''P. pauxi'' and ''P. unicornis'' were not conspecific. When Weske and Terborgh discovered the subspecies ''koepckeae'' they concluded ''pauxi'' and ''unicornis'' should be considered separate species. Additional studies by Gastañaga and coauthors in 2011 considered ''koepckeae'' to be a wholly distinct species on the basis of a somewhat smaller and more triangular crest and different vocalisations. Gastañaga ''et al.'' also coined the name Sira curassow as an English name for the bird in their 2011 paper; the name used by the local inhabitants for the bird is ''piuri''.

Other taxonomic suggestions discuss whether the genus ''Pauxi'' should stand alone or be grouped with other genera. In 1965 François Vuilleumier suggested the ''Pauxi'' species should be moved into a single genus alongside all the other species in the closely related genera ''Mitu'', ''Crax'' and ''Nothocrax''. Just two years later Charles Vaurie opposed this 'lumping' of species and argued that ''Pauxi'', ''Mitu'', ''Crax'' and ''Nothocrax'' should each be their own genera. Not content with either of these two options Delacour and Amadon suggested that ''Pauxi'' and ''Mitu'' should indeed be grouped with ''Crax'', but that ''Nothocrax'' was distinct enough to be its on genus. Many subsequent authors followed Vaurie, Delacour and Amadon in having ''Nothocrax'' as a sister clade to ''Pauxi'', ''Mitu'' and ''Crax'', while most have followed Vaurie in having the three other clades as three distinct genera.

Mitochondrial analysis conducted in 2004 suggests that ''P. unicornis'' is a sister species to ''Mitu tuberosum'', while the other ''Pauxi'' species, ''P. pauxi'', is sister to the combined ''Mitu'' and ''P. unicornis'' clade. This means the genus ''Pauxi'' is not monophyletic but paraphyletic, and to resolve this parsimoniously the genus ''Pauxi'' should be sunk into synonymy with ''Mitu''. The paraphyly of ''Pauxi'' could be due to incomplete lineage sorting, where a gene tree is inconsistent with its species tree, however this phenomenon should be less prevalent in deep phylogenetic splits (i.e. between genera). Because of this, Pereira ''et al.'' conclude incomplete lineage sorting is unlikely to account for the paraphyletic ''Pauxi'' genera because, according to their own analysis, ''Mitu'' and ''Pauxi'' diverged approximately 6.5mya.

Description

The horned curassow is among the largest cracid species. It measures in length.Horned Curassow ''Pauxi unicornis''
BirdLife International Body mass in large males is up to and only the great curassow is heavier amongst the cracids, although the black curassow and the closely related helmeted curassow are around the same length.Hughes, Nigel (2006) ''Curassows, Guans and Chachalacas'', Wildside Books (UK), Among standard measurements, the wing chord is , the tail is and the tarsus is . It has a distinctive horn or casque on the forehead which projects for over 6 cm. The plumage is generally black, but lacks a blue sheen in primary feathers, and has a white belly, thigh tufts and under-tail coverts. The tail also has white tips.

Status

The horned curassow is threatened by habitat loss. Until 2004 the horned curassow was classified as Vulnerable by the IUCN Red List due to a small and declining population, but was changed to Endangered in 2005 due to an estimated smaller range and greater risk from human activities. In Bolivia the potential habitat of subspecies ''P. unicornis unicornis'' may cover an area of 4,000 km² including the national parks: Amboró, Carrasco and Isiboro Sécure. Despite concentrated fieldwork there are many parts of this potential habitat in which no individuals have been found, for example the most north west 2,000 km².

References

Further reading

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*Hennessey, A.B. (2004a
Conservation presentations to Tacana communities within the last Bolivian site of the Wattled Curassow (Crax globulosa)
Bol. CSG 19: 9–13.
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*Mee, A. (1999
Habitat association and notes of the Southern Helmeted Curassow (Pauxi unicornis) in the Yungas of Cochbamba, Bolivia
Bol. CSG 9: 16–19.
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External links

* ttp://www.cracids.org/ Cracid Specialist Group
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horned curassow
Birds of the Yungas
Endemic birds of Bolivia
horned curassow
horned curassow
horned curassow
Taxonomy articles created by Polbot