The wattled curassow (Crax globulosa) is a threatened member of the family Cracidae, the curassows, guans, and chachalacas. It is found in remote rainforests in the western Amazon basin in South America. Males have black plumage, except for a white crissum (the area around the cloaca), with curly feathers on the head and red bill ornaments and wattles. Females and juveniles are similar but lack the bill ornamentation and have a reddish-buff crissum area. The wattled curassow is sister to other southern Crax curassows. In captivity, it sometimes hybridises with the blue-billed curassow. The habitat of the wattled curassow is gallery forests and seasonally-flooded forests where it feeds in small groups on the ground. The diet is largely fruit, but invertebrates and some small vertebrates are opportunistically taken. Little is known of its breeding habits, but it is known that the nest is built of sticks and leaves and two eggs are usually laid. The population of this species is declining. It is threatened by loss of habitat, as the rainforest is progressively cleared, and by hunting, and the International Union for Conservation of Nature has rated its conservation status as "endangered".
Description
The wattled curassow is about 82–89 cm (32–35 in) long, and weighs around 2,500 g (88 oz). It is a large curassow lacking the white tail-tips found in many of these birds; the feathers along the crest of its head are curled forwards. Males have black plumage all over except for the white crissum. The irides are dark brown; legs, feet and bill are blackish. It has conspicuous crimson bill ornaments—a round red knob with bony core adorns the maxilla base, while the cere extends apically at least halfway under this knob and below the mandible base forms a small fleshy wattle. Females have black plumage just like the male, but their crissal area is reddish buff. In some, the remiges and sometimes the wing coverts have faint brownish marbling. Their bills and irides are also blackish, but their feet and legs are a greyish flesh color. They lack the bill knob and wattles, and their cere is bright orange-red. Young males have less well-developed facial ornaments, usually with a more yellowish hue like females do. The hatchlings are covered in brown down above and whitish down below.
Similar species Adults look very much like those of the red-billed curassow (C. blumenbachii), whose males have only an indistinct maxilla knob. Its females have a blackish cere, rather pale legs and feet, and their wings—particularly the remiges—usually have distinct chestnut brown marbling. The black curassow subspecies C. alector erythrognatha, found north of the Solimões, has a cere like the wattled curassow female, but its bill is lighter and the crissum is white in both sexes. Young C. globulosa males are easily confused with those of the yellow-knobbed curassows (C. daubentoni), but the latter has a white tail-margin and yellow (not orange) bill wattle. All these similar species are allopatric however, with only C. a. erythrognatha occurring adjacent to the range of C. globulosa.
Taxonomy and systematics
The wattled curassow is one of the Crax species described in 1825 by Johann Baptist von Spix; the type locality is the Solimões (middle Amazon River) region. Crax is a term for curassows introduced by Mathurin Jacques Brisson in his 1760s Ornithologia and adopted by Linnaeus as a genus name in the Systema naturae. The specific name globulosa indicates the possession of one or more prominent round surface features (from Latin globus "a globe"). It has no recognized subspecies. According to cladistic analysis of multisequence mtDNA data, the wattled curassow is sister to other southern Crax curassows. Its origins date back some 6–5.5 mya ago (Messinian, Late Miocene) when its ancestors became isolated in the western Amazon rainforest. Some molecular phylogenetic analyses indicate a sister relationship with the red-billed curassow (C. blumenbachii), while others suggest that it is sister to a clade composed of C. blumenbachii, C. fasciolata, and C. alector. The similarity with the red-billed curassow seems to be mostly due to the fact that they have retained more plesiomorphic characters. Though externally still fairly alike, the two species have vastly different calls and probably evolved, at about the same time, at opposite ends of the original southern Crax curassow's range. From captivity, hybrids with the blue-billed curassow (Crax alberti) are known; the wattled curassow has also hybridized with black curassow (Crax alector) and bare-faced curassow (Crax fasciola). The yellow-knobbed curassow (C. daubentoni) is probably the most closely related to wattled curassow. But viable (though not dependably fertile) hybrids are suspected to be possible between any two species of Cracidae. The color and shape of the bill ornaments of male Crax hybrids are not easily predicted, but character displacement would demand the eastern (if any) subspecies of the black curassow (C. a. alector) to have a red ornamentation, as no red-ornamented congeners occur in or near its range. The red cere of the western black curassow may well be due to occasional hybrid introgression of C. globulosa alleles, as it is unlikely that the Solimões is entirely impassable to these birds.
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