Heliodoxa are medium large, heavy bodied hummingbirds with stout black bills that are more or less straight. The feathers of the forecrown extend onto the base of the maxilla, giving a somewhat tapered shape to the head. Most species are montane, and are sexually dimorphic. Most species of brilliant are mostly glittering green, but Fawn-breasted Brilliant is green only on the upperparts. The underparts of Fawn-breasted are primarily cinnamon buff, with green speckling on the throat and breast. Males have a small patch of pink on the center of the throat, but this usually is lacking in females.
Fawn-breasted Brilliant is distinctive within its range, and is unlikely to be confused with any other species: no other similarly sized hummingbird is green above and buffy below. Chestnut-breasted Coronet (Boissonneaua matthewsii) is deeper rufous below, with a green throat, and a shorter bill.
A medium large hummingbird with a long, heavy, straight bill. The following description is based on Hinkelmann (1999):
Adult male: Upperparts generally shining bronzy green; wing coverts more coppery. Rectrices coppery green and slightly forked. Chin green; center of lower throat rosy violet. Remaining underparts cinnamon buff, with scattered green disks on the throat and flanks.
Adult female: Similar to male, but chin cinnamon buff (not green), and usually lacks the rosy throat patch.
Iris: brown, dark brown, negro
Toes: brown, rosado
Bare parts color data from Miller (1963) and from specimens in the Field Museum of Natural History.
Total length: 11.2 cm (Hilty and Brown 1986); 10 cm (female), 11 cm (male) (Ridgely and Greenfield 2001b)
bill length, male: mean 2.24 mm ± .08 mm (n = 5; Colwell 2000)
bill length, female: mean 2.34 mm ± 0.10 mm (n = 6; Colwell 2000)
Mass: male, mean 8.0 g ± 0.4 g (n = 5; Colwell 2000); female, mean 7.6 g ± 0.3 g (n = 6; Colwell 2000)
female, 7.5 g (n = 1, rubinoides; Echeverry-Galvis et al. 2006)
male, mean 7.9 g (range 7.9-8.1 g, n = 3, aequatorialis; Miller 1963); female, mean 7.7 g (range 7.3-8.0 g, n = 3, aequatorialis; Miller 1963)
male, 6.0 g (n = 1, cervinigularis; Parker and O'Neill 1980); female, 7.0 g (n = 1; cervinigularis; Parker and O'Neill 1980)
mean (sexes combined?), 7.74 g (n = 8; Brown and Bowers 1985)