Tinamous are pudgy, terrestrial birds with short tails and wings; they superficially resemble tailless quail. The Little Tinamou is a small tinamou (20-24 cm, 250 g) with drab plumage. The plumage is mainly dark brown, with paler underparts. The crown is blackish, and the sides of the head are dark gray. There is slight sexual dimorphism in plumage, the female typically having brighter plumage than the male.
Little Tinamous overlap geographically with several other species of small Crypturellus tinamous, but Little Tinamou usually can distinguished by its small size and very plain plumage. Other species of Crypturellus in Central America (Slaty-breasted Tinamou C. boucardi, Thicket Tinamou C. cinnamomeus) are larger and have red tarsi. In South America, most geographically overlapping species of Crypturellus have plumage that is more or less obviously barred and are larger; some of these species also have red tarsi. The most similar species is the Brown Tinamou (Crypturellus obsoletus). Along the western edge of the Amazon Basin and in the Atlantic forest, the Brown Tinamou primarily occurs at higher elevations than Little Tinamou, although the two species may overlap in central South America. Brown also is a little larger than Little, with a gray (not white) throat, and more barring on the flanks.
Compare the Little Tinamou also to wood-quail (Odontophorus) and to quail-doves (Geotrygon).
The following general description of Little Tinamou is based on Blake (1977). Populations vary geographically; see also Geographic Variation.
Adult, male: Crown, nape, and sides of head dull black or blackish. Throat white, sometimes rufescent posteriorly. Upperparts generally dark grayish brown, olivaceous brown or rufous brown. Underparts paler, primarily ochraceous, cinnamon or rufous; the lower neck and breast usually more or less tinged with gray. Flanks with little or no dark barring; if present, barring is obscure.
Adult, female: Similar to male, but usually brighter and more rufescent.
Immature: Upperparts, and often the underparts as well, spotted with small whitish and black spots. Undertail coverts barred.
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Iris: gray, light brown, or orange
Bill: maxilla blackish; mandible gray or yellow with a darker tip
Tarsi and toes: greenish yellow or olive
Data from Blake (1977)
Total length: 20-24 cm (Howell and Webb 1995), 22-24 cm (Hilty 2003), 23 cm (Stiles and Skutch 1989)
Linear measurements (mm) of Crypturellus soui soui (Blake 1977)
| || || wing (flat)|| tarsus|| culmen (exposed)|
| male|| mean (n)|| 127 (10)|| 40 (1)|| 17.7 (10)|
| || range|| 117-137|| || 17-19|
| female|| mean (n)|| 136.4 (10)|| 39 (1)|| 19.5 (10)|
| || range|| 124-149|| || 17-21|
Measurements of other subspecies of Little Tinamou are in Wetmore (1965) and Blake (1977)
Mass: 220 g (Hilty 2003), 250 g (Stiles and Skutch 1989); male, mean 197.7 g ± 26.9 g (n = 6, range 164-244 g, Belize; Russell 1964); female, mean 235.4 g ± 17.1 g (n = 7, range 213-268 g, Belize; Russell 1964); female 174-238 g (n = 2, Suriname; Haverschmidt and Mees 1994)