The Ruddy Quail-Dove is a medium-sized (23.0-25.5 cm) columbid, with a typical quail-dove (Geotrygon) stocky build. Sexes differ in plumage. The upperparts of the male are primarily brownish rufous; the most distinctive feature is a brownish rufous stripe across the sides to the head, which are buff. The underparts are primarily buffy. The female is similar in pattern, but duller, with plive-brown upperparts.
Ruddy Quail-Doves are similar in size and shape to other species of quail-dove (Geotrygon), but the combination of overall brown or rufous-brown coloration and the dark stripe across the paler cheek is distinctive. The Ruddy Quail-Dove also can be confused with species of Leptotila, which also forage on the ground under vegetative cover; but all species of Leptotila have longer tails, which in most species also have prominent white tips to the outer rectrices; many species of Leptotila also have gray breasts and/or forecrowns, and no species of Leptotila has a stripe across the sides of the head.
The following description of nominate montana is based on Wetmore (1968); see also Ridgway (1916):
Adult male: Upperparts rufous-chestnut, paler on the forehead and wings; nape and back glossed with reddish purple. Throat and sides of the head pinkish cinnamon; sides of the head, below the auriculars, crossed by a reddish purple stripe. Breast vinaceous-fawn, turning to buff on belly. Sides and flanks cinnamon-buff to clay. Undertail coverts cinnamon-buff. Underside of wing cinnamon-rufous.
Adult female: Forecrown and sides of head dull cinnamon; sides of the head, below the auriculars, crossed by an olive stripe. Most of upperparts otherwise olive; primaries and greater wing coverts dusky, edged with cinnamon. Rectrices olive, except for blacker outer rectrices. Throat buffy white. Breast dull cinnamon to wood brown, changing to buff on belly; undertail coverts more cinnamon. Sides and flanks olive-brown. Underside of wing dull cinnamon-buff to dull rufous
Juvenile: Upperparts dark olive to dusky, forecrown paler. Tertials, wing coverts, remiges and rectrices tipped and edged with cinnamon. Breast olive-brown tipped with cinnamon, rest of underparts buffy white to buff. Males in this plumage are lighter and more brightly colored than females.
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Iris: very dark brown
Eyelids bright red; bare skin of lores and above and below eye, pinkish red
Cere: dull red
Bill: base of maxilla dull red, rest of maxilla and all of mandible warm brown
Tarsi and toes: anterior surface of tarsus, and toes, dark red; posterior surface of tarsus dull pinkish white
Bare parts colors from Wetmore (1968).
Total length: 21.0-23.5 cm (Wetmore 1968), 23 cm (Hilty and Brown 1986), 23-25.5 cm (Howell and Webb 1995)
Linear measurements (from Wetmore 1968):
male (n = 10): wing, mean 137.2 mm (range 143.2-141.1 mm)
tail, mean 70.5 mm (range 67.4-74.7 mm)
culmen, mean 12.0 mm (range 11.1-13.0 mm)
tarsus, mean 29.8 mm (range 28.2-31.8 mm)
female (n = 8): wing, mean 133.7 mm (range 132.2-138.8 mm)
tail, mean 69.9 mm (range 68.0-73.6 mm)
culmen, mean 11.3 mm (range 10.2-12.4 mm)
tarsus, mean 28.8 mm (range 27.2-29.7 mm)
Mass: 124.2 g ± 8.1 g (n = 13, Panama, sexes combined; Karr et al. 1978); mean 115 g, n = 62 (Peru; Dunning 2008).