The Black-throated Trogon is one of the smaller members of Trogonidae. In both sexes the lower breast and the belly are yellow, and the underside of the tail is barred black and white. The male has a green head, upper breast, and back, with a prominent bluish eyering. The areas colored green in the male are brown in the female; the female also has a bluish white area of bare skin just before and after the eye.
The Black-throated Trogon overlaps geographically with several other species of yellow-bellied trogon, including the Gartered Trogon (Trogon caligatus), from Honduras south to western Ecuador; the Amazonian Trogon (Trogon ramonianus), in much of the Amazon basin; and the Guianan Trogon (Trogon violaceus), in northeastern South America. Key differences include the colors of the upperparts and of the eyering. Males of the three other species have violet-blue upperparts and a yellow eyering; male Black-throated Trogons have green upperparts and a blue eyering. Female Black-throated Trogons are the only yellow-bellied trogons with brown upperparts.
The following description is based on Wetmore (1968); see also Ridgway (1911):
Adult, male: Crown, back, lesser wing coverts, rump, and upper breast metallic green. Forehead, sides of head, and throat black. Uppertail coverts somewhat bluish. Central rectrices bluish green to greenish blue, broadly tipped with black. Two adjacent pairs of rectrices similar on the outer web; inner web black. Three outer pairs of rectrices black, broadly tipped with white; the distal portions of the inner webs, and the outer webs, broadly barred with white. Primaries, primary coverts and inner webs of secondaries black, the longer primaries edged with white. Outer webs of secondaries, and the greater and middle wingcoverts black, finely vermiculated and barred with white. White band across the upper breast, below the metallic green. Lower breast and belly yellow.
Adult, female: Upperparts generally brown, usually darker on the crown and paler on the rump and uppertail coverts. Sides of the head like the crown. Central rectrices rufous-brown to chestnut; indistinct cinnamon-buff subterminal band, and a narrow black terminal band. Two adjacent pairs black, both outer and inner webs edged with rufous-brown to chestnut. Three outer pairs of rectrices black, tipped and heavily barred with white. Primaries and inner webs of secondaries fuscous-black, outer webs of primaries narrowly edged with white. Outer webs of secondaries, and greater and middle coverts, pale brown, with fine dusky vermiculations. Lesser wingcoverts black, tipped with brown. Throat and upper breast brown, usually paler than the back. White band across the upper breast, below the brown. Lower breast and belly yellow
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Iris: dark brown. Narrow eyering of male light blue; orbital ring of female white.
Bill: in male, mostly yellow or yellow-green; in female, black or blackish, with base (of both maxilla and mandible) yellow-green
Tarsi and toes: bluish gray
Data from Wetmore (1968)
Total length: 23 cm (Stiles and Skutch 1989), 24 cm (Hilty 2003), 23.5-26 mm (Wetmore 1968)
Linear measurements (mm) of Trogon rufus (Wetmore 1968)
| || || wing|| tail|| tarsus|| culmen from base|
| male|| mean|| 108.9|| 129.0|| 13.8|| 17.6|
| || range (n=18)|| 102.9-113.5|| 123.8-134.9|| 13.1-14.7|| 16.4-18.7|
| female|| mean|| 110.1|| 131.6|| 13.5|| 17.3|
| || range (n=15)|| 104.0-114.8|| 126.7-137.8|| 13.1-14.4|| 16.3-18.5|
Mass: males, mean 51.9 g (range 48-56 g, n=4); females, mean 55 g (range 52-57 g, n=3). Data from Suriname (Haverschmidt and Mees 1994). In southern Brazil, 1 male 57 g; 2 females, 54, 58 g (Belton 1984).