Bearded Mountaineer is a distinctive hummingbird of arid mountain slopes in southern Peru. The large size, long, forked dark and white tail, and white underparts make this species unmistakable. Males sport a brilliant long, green and pink beard-like gorget. Crown is bordered with whitish or with blue, depending upon subspecies.
Bearded Mountaineer is highly distinctive, and is unlikely to be confused with any other species of hummingbird within its limited geographic range. Andean Hillstar (Oreotrochilus estella) also has extensive white in the tail, but occurs at higher elevations, has a shorter rounded tail, and does not have the prominent pale supercilium of Bearded Mountaineer.
The following description is based on Zimmer (1953), Meyer de Schauensee (1970). Fjeldså and Krabbe (1990) and Fjeldså (1999), and refers to nominate nobilis; see also Geographic Variation:
Adult male: Forecrown and crown deep purplish blue, with a narrow black medial stripe. Sides of head and throat otherwise mostly bronzy black, bordered posteriorly by a narrow white band that connects to the white of the breast. Nape, back and rump bronzy or bronzy brown. Tail long and deeply forked; central pair of rectrices bronzy, the outer rectrices bronzy and white, the amount of white increasing laterally, with the outermost pair almost entirely white. Long narrow gorget (beard like) emerald green basally, and purplish distally, with a bluish tip. Center of the breast white, sides of breast and flanks more or less brown; undertail coverts bronzy brown.
Adult female: Similar to adult male, but duller; gorget reduced in size, often scaled with white basally, and with little or no purplish or blue. Tail less deeply forked. Underparts dingier.
Juvenile: Duller, with yellow mandible. Hood dull, with green crown, somewhat scaled. Throat dull brown. Rictal stripe and lores mottled with white.
Iris: coffe brown, black
Bill: black in adults; mandible yellow mandible in juveniles
Bare parts color data from specimens in the Field Museum of Natural History and from Fjeldså and Krabbe (1990).
Total length: 14-17 cm (Fjeldså and Krabbe 1990), 15.5–16.5 cm (Schulenberg et al. 2010)
Bill length: 2.2 cm (Fjeldså and Krabbe 1990), 2.3 cm (Colwell 2000), 2.4 cm (Schulenberg et al. 2010)
Wing length: 85 mm (Berlioz 1938; n = 1)
Tail length: 85 mm (adult male) (Berlioz 1938, Fjeldså and Krabbe 1990), 65 mm (juvenile) (Fjeldså and Krabbe 1990)
Mass: mean 7.7 g (n = 3, sex?, range 7-9 g; Brown and Bowers 1985, Colwell 2000)