The White-winged Guan is a guan of general black coloration, with an iridescent green gloss. The primaries are white, contrasting with the black color of the rest of the body. The tail and legs are long. Short longitudinal white streaks are present on the head, neck and upper back, and also extend from the breast to the base of the legs.
Within the known distribution of the White-winged Guan, the only other sympatric cracid species is the Bearded Guan (Penelope barbata). These two species are mostly separated by elevation, but overlap for about 100 m elevational, at the upper limit of the elevational distribution of albipennis.
The Bearded Guan is smaller, is brown (not blackish), and does not have white on the wings. The tarsi of the Bearded Guan are red, and bare parts on the face are less conspicuous.
Crested Guan (Penelope purpurascens) is found in the extreme north of Tumbes department, in the Pacific tropical forest. There is no known overlap in the distribution of both species. Crested Guan is more brownish, and has no white on the wings. The bare parts on the face of Crested Guan are darker.
Adult: Sexes similar. General coloration blackish brown, the plumage with shiny green gloss. Feathers of crown, neck, upper back, and breast with narrow, whitish or pale gray edges, forming short streaks; this pattern extends on the belly to the base of the legs. The outermost nine (or, sometimes, eight) primaries white, contrasting markedly with the dark body coloration; these white primaries have dusky tips and bases, but are white for most of their length.
The adult White-winged Guan molts once a year between July and September; this is the dry season, when the guans are not breeding.
Iris: Reddish in adults, light brown in juveniles.
Bare facial skin: Purple
Gular wattle: Orange
Bill: Dark gray, with black tip.
Tarsi and toes: Orangeish or pinkish.
Mean measurements (n=80, live specimens; FAP data):
Total length: 85.2 cm
Wing length: 36.3 cm
Tail length: 35.8 cm
Bill length: 3.3 cm
Tarsus length: 8.1 cm
Head: 8.3 cm
Body: 40.8 cm
Mass: 1.6 kg