Manacus are small, short tailed manakins. Both sexes have orange tarsi and toes, and males have elongated feathers on the throat. Females of all species of Manacus are dull olive; males of all species have a black crown and wings and a broad pale collar across the nape and upper back, but the color of the body plumage is variable across species, in various combinations of white, yellow or orange, and pale olive. The male White-bearded Manakin is the whitest member of the genus: the upperparts are mostly black, except for the broad nape collar and a gray rump, and the underparts are almost entirely white, with a gray wash, variable in intensity, on the belly and flanks.
Male White-bearded Manakin is distinctive across most of its range, and unlikely to be confused with any other species. It is most similar to White-collared Manakin (Manacus candei), but the geographic distributions of these two species do not overlap; also, male White-collared Manakin has a bright yellow belly. There is contact (and limited hybridization) between White-bearded Manakin and Golden-collared Manakin (Manacus vitellinus) in western Colombia. As the name suggests, the white of the collar, throat and breast of White-bearded Manakin is replaced in male Golden-collared Manakin by bright deep yellow, with a green belly. Females of the two species are quite similar, but female Golden-collared Manakin has a yellow tinge to the belly, which is more olive in female White-bearded.
Female White-bearded Manakin also is similar to female Chiroxiphia and Antilophia manakins, but is smaller, with tarsi that are more orange; also, Antilophia have longer tails, and the females of some species of Chiroxiphia (Lance-tailed Manakin C. lanceolata and Swallow-tailed Manakin C. caudata) have elongated central rectrices.
The following description is based on Kirwan and Green (2011), and refers to nominate manacus; see also Geographic Variation:
Adult male: Crown deep black. Sides of head (including the auriculars) and of neck, and broad collar across nape, white (constrasting sharply with the black of the crown). Back, wings and tail deep black. Rump and uppertail coverts dark gray. Throat and breast white (and connected to the white nape collar); belly and flanks white, with a gray cast.
The feathers of the throat are somewhat elongated (and can be projected forward during displays). Most remiges are stiffened, with thickened, bowed shafts and stiff outer webs. Additionally, the distals portions of four outer five primaries are very narrow and stiff.
Adult female: Upperparts olive green. Underparts paler and grayer, especially on the throat and belly.
Juvenile: Very similar to adult female; body plumage fluffier. "Young males" (age?) may have dark shaft streaks on the crown.
Bill: maxilla black, mandible blue gray, gray, or brown
Tarsi and toes: orange yellow, yellow orange
Bare parts color data are from Junge and Meise (1958), Haverschmidt (1968), Wiedenfeld et al. (1985), and Novaes and Lima (1998).
Total length: 10.2 cm (Hilty and Brown 1986), 10.7 cm (Hilty 2003), 10–11 cm (Schulenberg et al. 2010), 11 cm (Ridgely and Greenfield 2001b)
Linear measurements (from Kirwan and Green 2011, who provide additional mensural data; see also Hellmayr 1929, Friedmann 1944, Glydenstolpe 1945, Junge and Mees 1958, and Oniki and Willis 1999):
wing length (n = 7), 55-56 mm
tail length (n = 7), 28.5-33.0 mm
bill length (n = 2), 11.95-12.41 mm
tarsus length (n = 7), 16.82-22.32
wing length (n = 7), 54-59 mm
tail length (n = 7), 32-35 mm
tarsus length (n = 7), 18-21 mm
wing length (n = 13), 51.0-57.5 mm
tail length (n = 13), 30-37 mm
bill length (n = 13), 10.94-12.67 mm
tarsus length (n = 4), 19.14-20.97
wing length (n = 4), 53.5-55.0 mm
tail length (n = 4), 31-35 mm
bill length (n = 4), 12.44-13.38 mm
tarsus length (n = 3), 16.85-18.76 mm
wing length (n = 13), 50.5-55.0 mm
tail length (n = 13), 28-35 mm
bill length (n = 13), 10.81-14.06 mm
wing length (n = 3), 52-55 mm
tail length (n = 3), 30-35 mm
bill length (n = 3), 11.75-11.96 mm
wing length (n = 10), 52.0-58.5 mm
tail length (n = 10), 32-39 mm
bill length (n = 10), 10.66-12.58 mm
tarsus length (n = 7), 19.54-20.42
wing length (n = 6), 49-55 mm
tail length (n = 6), 31-40 mm
bill length (n = 6), 11.33-12.41 mm
tarsus length (n = 5), 17.31-20.35
Mass: manacus, male, mean 17 ± 2 g (range 14-20 g, n = 5; Dick et al. 1984); female, mean 15.5 g ± 3 g (range 12-20 g, n = 4; Dick et al. 1984). Additional data on mass is provided by Kirwan and Green (2011).