Aracaris (Pteroglossus) are small, slender toucans. The plumage typically is black, brown, or dark green above, with a black head and red rump, and the underparts usually are extensively yellow. Aracaris have exposed pale skin around the eye, and a long, slender, toucan bill, the maxilla of which is serrated. Collared Aracari is a typical representative of the genus. The head, throat, breast, and upperparts are black, with an inconspicuous cinnamon rufous band (collar) across the nape, and bright red lower back, rump, and uppertail coverts. The underparts are yellow. There is a red wash on the breast, and the breast also has a black central spot. A narrow band of red and black crosses the belly, and tibial feathers are cinnamon rufous or rufous. The bare facial skin is red. The base of the bill has a narrow white vertical band. The maxilla is pale grayish horn or whitish, with a black culmen and tip, and variably reddish at the base; the mandible is black. Two South American subspecies lack the cinnamon rufous nuchal collar, and have slightly different patterns on the bill (see Geographic Variation).
Collared Aracari is the only species of Pteroglossus in most of its range, and so it is not likely to be confused with other species: Yellow-throated Toucan (Ramphastos ambiguus), Keel-billed Toucan (Ramphastos sulfuratus), and Choco Toucan (Ramphastos brevis) all are much larger, with a larger, more brightly colored bill, and have a bright yellow throat and breast (among many other differences). Collared Aracari is replaced on the Pacific coast of Costa Rica and northwestern Panama by Fiery-billed Aracari (Pteroglossus frantzii); these two species occasionally hybridize. The plumage of both species is very similar, but the black breast spot of Fiery-billed is larger, and the belly band is broader and is entirely red, with no admixture of black. The most striking difference is the color of the maxilla, which, as the English name suggests, is deep orange to vermilion in Fiery-billed Aracari.
The following description is based mostly on Ridgway (1914) and Wetmore (1968); see also Short and Horne (2001):
Adult male: Upperparts primarily glossy black, with a narrow cinnamon rufous nuchal collar; the head, throat, and uppermost breast are a greenish black, whereas the back, scapulars, wing coverts, and rectrices are olivaceous black. Lower back, rump, and uppertail coverts bright red. The lower breast, belly, and undertail coverts are primarily yellow. There is a red wash, variable in extent, on the breast, and central black breast spot, also variable in size. A narrow band, variable in size, of red mixed with black crosses the upper belly. The tibial feathering is cinnamon rufous or rufous. Underwing coverts white to grayish white or pale yellow. Bases of remiges dull yellowish white. The bill is long and deep, hooked at the tip and with many coarse serrations along the tomia of the maxilla.
Adult female: Extremely similar to the male. Differs only by "a small spot of rufous hidden on the bases of the auricular feathers" (Wetmore 1968) or by having a darker (chestnut) nuchal collar (Short and Horne 2001). As is typical of toucans in general, the bill of the female also is shorter (Short and Horne 2001; see Measurements).
Immature: Wetmore (1968), probably following Ridgway (1914), describes the juvenile as similar to the adult, but lacking serrations on the maxilla; this may refer to a Formative Plumage, however. Stiles and Skutch (1989) describe the "young" (presumably meaning juvenile) as "much duller [than adult]: head and chest sooty-black; back dark brownish-olive; rump duller red; below pale yellow with indistinct breast-spot and band" (see also Short and Horne 2001). The bill also has a less distinct pattern (see Bare Parts).
There is little information on molts in Collared Aracari (or in Ramphastidae in general), but it apparently follow the Complex Basic Strategy, with a partial Preformative Molt but no Prealternate Molt. The Preformative Molt includes a complete body molt, but the juvenile flight feathers (remiges and rectrices) are retained (Dickey and van Rossem 1938). In El Salvador, the Prebasic Molt "commences very early (as early as June 11 in one specimen)" (Dickey and van Rossem 1938). Molt of the rectrices "commences with third or fourth pair from the outside and progresses outwardly. The central pair usually are not shed until the other rectrices are nearly, sometimes fully, grown" (Dickey and van Rossem 1938).
Iris: bright yellow, pale yellow, or yellowish gold; area just anterior to and just posterior to, pupil is dark green, giving the effect of a pupil in shape of a horizontal slit or oval
Facial skin: reddish orange, dark red, or red; narrowly black around the eye, but the extent of black is variable, and the entire area between the eye and maxilla can be black. Facial skin of immatures is yellowish orange, pale blue, or pale brown to white.
Bill: Narrow vertical white line at base of bill. Culmen, tip of maxilla, and the bases of notches on the maxilla black; tips of notches on tomia of maxilla clear yellowish white. Sides of maxilla buffy white, shading through dull green to dull reddish brown basally. Mandible black.
Bill of immature lacks notches, the white basal vertical line, and generally is unpatterned or is blotchy with yellow, and with some greenish brown or greenish black. It can take up to a year for the adult pattern to develop.
Tarsi and toes: dull green; claws black. Tarsi of immatures yellow to green.
Bare parts color data from Dickey and van Rossem (1938), Wetmore (1968), and Short and Horne (2001).
Total length: 38-43 cm (Howell and Webb 1995), 41 cm (Stiles and Skutch 1989)
Linear measurements (from Short and Horne 2001; nominate torquatus):
- wing length: mean 146.1 mm (range 136-159 mm; n = 78)
- tail length: mean 157.2 mm (range 137-170 mm, n = 70)
- bill length: mean 104.02 mm (range 93-123 mm, n = 86)
- tarsus length: mean 34.91 mm (range 31.8-37.4 mm, n = 87)
- wing length: mean 145.0 mm (range 133-160 mm; n = 61)
- tail length: mean 154.3 mm (range 137-184 mm, n = 52)
- bill length: mean 93.41 mm (range 79-102 mm, n = 66)
- tarsus length: mean 34.44 mm (range 30.5-37.0 mm, n = 67)
Mass from Short and Horne 2001; nominate torquatus):
male: mean 228.7 g (range 175-254 g, n = 25); female: mean 216.4 g (range 183-246 g, n = 19)
Mean brain volume, 3500 mm3 (n = 10, Mlikovsky 1989)