Lettered Aracari is a small aracari that is primarily green, black, and yellow. The male has a black hood. The back, wings, and tail are dark green, and the breast and belly are dusky yellow. The rump is red. The female is similar in pattern, but the hood is mostly chestnut, with a black crown and nape. Lettered Aracari has the typical long and deep toucan bill. The maxilla is primarily pale yellow or creamy yellow, with a series of vertical marks ("letters") along the tomia, and a black tip; the pattern of the mandible varies geographically, and may be primarily pale yellow or (in the eastern subspecies) entirely black. Immature Lettered Aracaris are duller, with more subdued bill markings.
Lettered Aracari is the only species of aracari within its range that has an entirely yellow breast and belly; other species that overlap geographically have red, black, or red and black bands across the breast or belly. Other species of aracari also differ in many other features, including the color pattern on the bill. Ivory-billed Aracari (Pteroglossus azara) is another widespread, small species of aracari that also has an extensively pale bill, with black marks along the tomia; but the bill of Ivory-billed Aracari is more cream (less yellow), the black marks along the tomia are much smaller and less conspicuous than in Lettered, and Ivory-billed Aracari has a broad red breast band.
Green Aracari (Pteroglossus virdis) of the Guianas is similar to Lettered Aracari in plumage pattern, but these two species do not overlap geographically. Green Aracari has a different color pattern on the bill: the maxilla is chestnut red, with a broad yellow stripe along the top, and lacks the "letter" markings), and the base of the mandible also is reddish.
The following description is based on Short and Horne (2001), and refers to nominate inscriptus; see also Geographic Variation:
Adult male: Entire head (including the throat) black, except for bare orbital skin (see Bare Parts). Back, wings, and rectrices dark green; rump crimson. Breast, belly, and undertail coverts yellow, variably blotched with pale buff cinnamon, especially on the lower breast and upper belly. Tibial feathers variably, from almost entirely green to roughly half green and half pale whitish yellow.
Adult female: Similar in pattern to adult male, but the sides of the head and neck, and the throat, are chestnut rather than black; there also is narrow black band at the lower border of the chestnut on the throat. Bill also shorter than in the male (see Measurements).
Immature: Similar to the adult of the respective sex, but plumage looser. Plumage also paler on the back and underparts, especially on the rump, which is duller red. Yellow feathers of underparts usually with some buff to cinnamon tipping.
Undescribed; probably follows the complex basic molt strategy.
Iris: red to brown red
Orbital skin: broad area of bare skin surrounding the eye, blue above and before the eye, darker, more violet gray below the eye, and with a red triangular mark behind and below the rear of the eye
Bill: maxilla primarily pale yellow, with a narrow black base that connects to a narrow black stripe along the culmen and a broad black tip; also a series of narrow vertical "script" marks along the tomia. Mandible pale yellow with a broad black base and a black tip, and a few vertical "script" marks just proximal to the black tip
Tarsi and toes: blue to green or olive green; toe pads yellow
Bare parts color data from Short and Horne (2001), and refer to nominate inscriptus; see also Geographic Variation.
Total length: 33-35.5 cm (Ridgely and Greenfield 2001b), 37 cm (Hilty and Brown 1986)
Linear measurements (from Short and Horne 2001):
wing length: mean 117.3 mm (range 119-125 mm; n = 32)
tail length: mean 127.9 mm (range 115-141 mm, n = 31)
bill length: mean 76.8 mm (range 68.8-88.7, n = 36)
tarsus length: mean 28.7 mm (range 26.7-31.0, n = 32)
wing length: mean 125.4 mm (range 117-140 mm; n = 28)
bill length: mean 83.4 mm (range 75.0-102, n = 30)
wing length: mean 111.2 mm (range 106-118 mm; n = 31)
tail length: mean 123.5 mm (range 111-134 mm, n = 28)
bill length: mean 69.4 mm (range 59.0-78.8, n = 33)
tarsus length: mean 28.1 mm (range 24.7-30.2, n = 27)
wing length: mean 123.7 mm (range 117-132 mm; n = 23)
bill length: mean 73.4 mm (range 61.0-91.4, n = 30)
Mass (from Short and Horne 2001):
male, inscriptus: mean 120.8 g (range 102-140 g, n = 11)
male, humboldti: mean 146.6 g (range 111-185 g, n = 11)
female, inscriptus: mean 112.4 g (range 95-130 g, n = 8)
female, humboldti: range 122-166 g (n =3)