Family Guans, Chachalacas, Curassows (Cracidae)

Critically Endangered

Horned Curassow (Pauxi unicornis)

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Taxonomy

French: Hocco unicorne German: Hornhokko Spanish: Paují unicornio boliviano
Other common names: Bolivian Helmeted Curassow
Taxonomy:

Pauxi unicornis

J. Bond and Meyer de Schauensee

, 1939,

above Bolívar, near Palmar, Yungas de Cochabamba, Bolivia

.

Has been considered a race of P. pauxi, and until very recently was treated as conspecific with P. koepckeae, but differs from latter in its upright, columnar vs backward-sloping, ellipsoid casque (3); broad vs narrow white tips of outer rectrices, with white-tipped vs all-black central rectrices (2); song consisting of eight notes forming four phrases with emphasis on last note vs four notes in single phrase over 3–4 seconds#R (3); up-and-down pumping vs horizontal fanning of tail in alarm (1). Monotypic.

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Distribution:

E slope of Andes in C Bolivia (Cochabamba and Santa Cruz). In 1992, a bird of undetermined affinity was seen in Cerros de Távara, in S Peru, halfway between known ranges of P. koepckeae and P. unicornis, and has hence been suggested that one or both species may be present on low Andean foothills and outlying ridges from Cerros del Sira S into Bolivian Yungas; Távara record, however, has since been discounted#R.

In 1992, a bird of undetermined affinity was seen in Cerros de Távara, in S Peru, halfway between known ranges of P. koepckeae and P. unicornis, and has hence been suggested that one or both species may be present on low Andean foothills and outlying ridges from Cerros del Sira S into Bolivian Yungas; Távara record, however, has since been discounted#R.

Descriptive notes

85–95 cm; male c. 3850 g; female c. 3600 g. Large, virtually all-black cracid with white vent and tip to tail. Bright red bill and pale blue casque, which grows up to 6·3 cm#R. Legs normally pale red, but yellowish in male during breeding season. Sexes alike, with purported differences in casque shape and bare-part colours subject to overlap#R, but female also has a rufous colour phase (as in P. pauxi). Separated from entirely allopatric P. pauxi by shape of casque, deeper bill and presence of short, tightly curled, glossy crest; from Peruvian P. koepckeae by longer, broader, bluer casque tilted farther back, greenish (rather than bluish) sheen to the plumage#R, and white on tips of central rectrices; vocalizations also differ#R.

Drawing by Francesc Jutglar
Descriptive notes:

85–95 cm; male c. 3850 g; female c. 3600 g. Large, virtually all-black cracid with white vent and tip to tail. Bright red bill and pale blue casque, which grows up to 6·3 cm#R. Legs normally pale red, but yellowish in male during breeding season. Sexes alike, with purported differences in casque shape and bare-part colours subject to overlap#R, but female also has a rufous colour phase (as in P. pauxi). Separated from entirely allopatric P. pauxi by shape of casque, deeper bill and presence of short, tightly curled, glossy crest; from Peruvian P. koepckeae by longer, broader, bluer casque tilted farther back, greenish (rather than bluish) sheen to the plumage#R, and white on tips of central rectrices; vocalizations also differ#R.

Voice

Peak singing period, and therefore probably breeding, at start of wet season (several months earlier than that of P. koepckeae, which peaks at end of wet season). Song, which lasts c. 9 seconds, typical of genus and apparently given only by males (although further research may prove otherwise, as with several other curassows of varied genera), usually from a perch (rarely from the ground)#R, a humming “hmm-mmum...HM” that at some distance (the song is rarely audible >150 m away) is indistinguishable from the locally syntopic Mitu tuberosum, which is more trisyllabic#R; much longer (with more phrases, more notes) than song of P. koepckeae and with distinctive loud final note. Sings most frequently just before and after dawn (04:00–07:00 hours)#R, at rate of c. 4 songs/minute usually for a mean duration of c. 1 hour#R. Neighbouring booming males sometimes synchronize their songs#R. Alarm call, a sharp, explosive “k-sop!”#R or “kseeuk”, is given either from ground or on perch after being flushed from ground#R; usually accompanied by vertical tail-pumping (horizontal tail-fanning in P. koepckeae).

Habitat

Dense lower montane forest, with heavy rainfall, usually in rugged hilly country between 400 m and 1300 m#R with most records at 500–900 m#R. Area of suitable habitat very small, both geographically and elevationally#R. In Amboró National Park (Santa Cruz), birds were found in semi-open tropical forest on steep slopes, usually with a relatively open understorey and sometimes in vicinity of watercourses#R, but occasionally wanders into regrowth, and males can hold territory in areas with relatively gentle slopes#R.

Food and feeding

Diet consists of fruit, seeds, soft plants, and adult and larval insects; has been estimated that composition may be 25% fruits, 50% invertebrates and 25% vertebrates#R. Fallen nuts of almendrillo (almond tree) apparently constitute major food; hard shell disintegrates, allowing birds to access seeds. Presumably also takes other fruits fallen from trees; three types of laurel (Nectandra) and negrillo (Lauraceae) reported as food by locals, and Ficus-like seeds found in faecal sample#R. Also reported to take young shoots, invertebrates (particularly larval Coleoptera and adult Diptera) and bones of small mammals#R. Female on nest took flying insects while incubating#R. Forages mainly from dawn to 08:30 hours, and from 16:00 hours to dusk, but feeding observed throughout day#R; previous reports that species forages at night have since been discounted for want of evidence#R. May escape predators by gliding downhill (perhaps aided by cliffs, banks and steep ridges), although it may also also take refuge in trees, walk away or flee uphill.

Breeding

Activity (nuptial calls) begins with start of rains, in Sept, in Amboró National Park. Apparently polygynous, and species has been postulated to display at dispersed leks, although other observers have suggested that males are territorial and monogamous#R. Only one nest found to date, in Oct at Amboró National Park: a substantial (c. 30 cm wide) bowl-shaped#R structure of dead leaves and twigs#R placed 5 m up in fork of an isolated tree surrounded by water#R, containing only one egg; incubation apparently by female alone#R; chick rich brown, marked with black above, buff and whitish below; helmet becomes visible at just one month of age#R. On basis of casque sizes, it is believed that first-year birds participate in courting and breeding.

Movements

Presumably sedentary, but in Amboró National Park some dispersive movements have been reported at end of breeding season.

Status and conservation

CRITICALLY ENDANGERED. Estimated total population in range 1000–4999 mature individuals, equating to c. 1500–7500 individuals in total. Confined to Bolivia, where locally distributed: known from Amboró and Carrasco National Parks#R#R#R, and more recently found in Isiboro-Secure Indigenous Territory and National Park and at outer edge of Cordillera Mosetenes (Cochabamba). Formerly occurred along entire N boundary of Carrasco National Park, but in recent surveys it was recorded in very few locations there; extensive searches over several years have failed to find this cracid in Madidi National Park (La Paz), in the R Tambopata area near Peru–Bolivia border#R and in Cordillera Cocapata and along inner edge of Cordillera Mosetenes (Cochabamba). Small global range (variously estimated at 4000 km² and 10,244 km²)#R and known from very few locations, all in narrow altitudinal band which is subject to habitat loss; believed to be declining extremely rapidly as a result of hunting and habitat destruction. Can occurs at densities of up to 20 individuals/km², although this appears to be exceptional and at most sites just one or two individuals found#R. Forests in this species’ altitudinal range are rapidly being cleared for growing of crops by recent settlers from Altiplano#R,#R, while road-building and associated developments have adverse effect and make it more difficult for individuals to disperse#R. Greatest threat, however, appears to be that of hunting for food by local inhabitants, which is almost certainly exerting a very serious adverse impact on this cracid throughout its fragmented range. At least formerly, in Yungas of Totora (Cochabamba), this cracid was hunted also for its casque, which was used as a fashionable cigarette-lighter, and in Amboró area, its skewered head was apparently used in traditional dances. Both human encroachment, primarily for cultivation (including of coca), and severe hunting pressure (including from professional hunters) continue to increase throughout Bolivia, even in national parks, which lack effective protection, and it is predicted that, unless massive concerted conservation measures can be achieved, this species may become extinct in the wild within 30 years at most.

Recommended citation

del Hoyo, J., Kirwan, G.M. & Christie, D.A. (2017). Horned Curassow (Pauxi unicornis). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/53310 on 22 June 2017).