The Giant Conebill is a stout passerine with a long pointed bill. Back and wings are blue-gray, with chestnut throat, belly and underparts. Forecrown whitish; the nominate subspecies has a chestnut eyestripe and black malar, but there is significant variation in the facial pattern.
Nearly unmistakable plumage and distinctive behavior. Similar in color and pattern to the White-browed Conebill (Conirostrum ferrugineiventre); C. ferrugineiventre is smaller, lacks the distinctive white cheek-patch, and generally occupies lower elevations, although the two do occasionally overlap and have been known to hybridize (Schulenberg 1985). Oreomanes also bears a behavioral resemblance to Sitta nuthatches, sometimes hanging upside down while foraging (George 1964). Chestnut underparts and dark mantle might suggest Black-throated Flowerpiercer (Diglossa brunneiventris), however the Giant Conebill’s chunkier stature and association with Polylepis woodland serve to distinguish the two (Jaramillo 2003).
Adults: Monochromatic species, male and female plumages indistinguishable. Adults have plumbeous backs and wings, with a chestnut throat, belly and crissum. Face has a large white cheek patch, generally with a dark chestnut eyeline and patch around eye, defining a thin white supercilium (Jaramillo 2003). Rounder body than other passerines, and a long, sharply pointed bill.
Immature: Crown mostly dusky; lower cheek, throat and supercilium white, throat mottled with blue-gray spots, and underparts slightly lighter russet than adult plumage (Fjeldså and Krabbe 1990).
Juvenile: Similar to immature, but browner on back and wings with a whiter throat (Fjeldså and Krabbe 1990).
Little is known regarding the timing and sequence of molts in the Giant Conebill, but juveniles are distinguishable from parents for at least five weeks after hatching (Cahill et al 2008).
Iris: Brown (Schulenberg 1985)
Bill: Dark slate to black, mandible sometime described as paler than maxilla (Schulenberg 1985)
Tarsi: Gray-brown, dark gray, black (Schulenberg 1985)
Total length: 15 cm (6 in.) (Isler and Isler 1999).
Mass: mean 25 g (range 22.0–27.0 g, n=25) (Vuilleumier 1984, Isler and Isler 1999).
Table taken from Vuilleumier (1984).