Maroon-fronted Parrot is a large long tailed parrot, resembling a small macaw in size and shape. It primarily is bright green on the upperparts and underparts, with a dark brownish maroon forehead, supercilium, and lores, bright red carpal patches and thighs. The under surfaces of the remiges and rectrices are dark brownish gray, although the underwing coverts are bright green. The adult has a dark bill and orange-yellow irides surrounded by a yellowish white orbital ring, and dark gray toes. The juvenile has a paler horn bill and a brown iris.
Maroon-fronted Parrot is very similar to the congeneric Thick-billed Parrot (R. pachyrhyncha). Thick-billed Parrot is slightly smaller, is slightly paler green, has scarlet rather than brownish maroon forehead, lores and supercilium, and has yellow greater underwing coverts. These two parrots are allopatric, and so rarely overlap.
Military Macaw (Ara militaris) is much larger than Maroon-fronted Parrot with a proportionally longer tail; has a turquoise rump, uppertail coverts, and remiges; and the rectrices are red and blue.
The following description is based on Juniper and Parr (1998) and Howell and Webb (1995):
Adult: Sexes similar. Plumage primarily green, with a brownish olive suffusion. Forecrown, most of the lores, and a narrow stripe over the eye dark brownish maroon; small dark brown patch on lores, directly in front of the eye. Crown, auriculars, and sides of the neck bright green. Upper surface of rectrices green; under surface of rectrices brownish gray. Upperwing coverts greenish olive; red patch on carpal area. Remiges greenish olive above, with darker tips and inner webs; undersurface of remiges dark brownish gray. Underwing coverts yellow olive. Tibial feathers maroon or dark red.
Juvenile: Poorly known. Juvenile of the closely related Thick-billed Parrot (Rhynchopsitta pachyrhyncha) is similar to the adult, but lacks the red on the wings and face, and the red of the thighs is reduced (Snyder et al. 1999); juvenile Maroon-fronted Parrot may be similar. Also differs from adult in color of the bare parts.
Iris: orange yellow or amber in adult; brown in juveniles. Orbital ring skin is yellowish white or grayish buff.
Bill: black to dark olive black in adult; paler,horn with gray at base of upper mandible in juvenile
Tarsi and toes: gray or dark gray
Data for bare parts from Juniper and Parr (1998) and Howell and Webb (1995).
Total length: 40-45 cm (Juniper and Parr 1998), 40.5-45.5 cm (Howell and Webb 1995)
Linear measurements (from Forshaw 1989):
male (n = 4)
wing length: mean 287.8 mm (range 287-290 mm)
tail length: mean 193.8 mm (range 185-204 mm)
bill length (exposed culmen): mean 41.3 mm (range 40-42 mm)
tarsus length: mean 23.8 mm (range 23-24 mm)
female (n = 1)
wing length: 283 mm
tail length: 188 mm
bill length (exposed culmen): 40 mm
tarsus length: 24 mm
Mass: male, mean 429.5 g (n = 2: 391.5 g, 467.5 g; Urban 1959); female, 466 g (n = 1; Urban 1959)