Appearance

Nighthawks and nightjars are primarily nocturnal birds with very cryptically patterned, soft and lax plumage. All species have short bills with very wide gapes and conspicuous rictal bristles. They have very weak feet with a comb-like structure on the nail of the middle toe. Lurocalis nighthawks have longer, scimitar shaped wings than Chordeiles nighthawks, and in flight the wings of Lurocalis nighthawks are held straigher, lacking the obvious bend at the "wrist" that is so characterisitic of Chordeiles. Lurocalis also have very short tails and a pale patch on the scapulars and inner secondaries.

The sexes of Rufous-bellied Nighthawk are similar. The upperparts are dark dusky brown, with numerous small rufous or tawny spots. The throat is white. The breast is similar to the upperparts, dusky brown with tawny spots, but the belly is tawny buff. There are no white markings on the wings or tail.

Rufous-bellied Nighthawk is most similar to Short-tailed Nighthawk (Lurocalis semitorquatus), so much so that Rufous-bellied previously was considered to be a subspecies of Short-tailed Nighthawk. Rufous-bellied Nighthawk is significantly larger than Short-tailed, and has different vocalizations. The unbarred rufous belly of Rufous-bellied Nighthawk also distinguishes this species, although this feature is not always readily visible under field conditions. Also note that these two species have different elevational distributions, with Short-tailed Nighthawk confined to the lowlands (usually below ca 1000-1100 m), and Rufous-bellied Nighthawk only in the Andes, usually above 1400 m.

The following description is based on Cleere (1998):

Adult: Sexes similar. Forecrown, crown, and nape dark brown, spotted and speckled with rufous and buff. Back, rump and uppertail coverts dark brown, spotted and speckled with rufous and buff. Scapulars grayish white, mottled with brown. Primary coverts dark brown, barred with deep cinnamon rufous; remaining wing coverts dark brown, varieagated with rufous, tawny, buff, and grayish white. Primaries brown, boldly ocellated with tawny along the outer webs, and barred grayish brown along the inner webs; inner primaries narrowly tipped buffish or grayish white. Secondaries brown, spotted with tawny, and barred and narrowly tipped with grayish white. Tertials brownish white, mottled with brown. Rectrices brown, barred with tawny or grayish brown, and narrowly tipped with brownish buff (central and two outer pairs: R1, R4-R5) or whitish (rectrice R2-R3). Lores and auriculars dark brown, spotted with rufous. Chin and sides of throat dark brown, barred with white. Throat white. Upper breast dark brown, faintly spotted and barred with pale tawny; lower breast barred grayish white. Belly and flanks tawny buff. Undertail coverts tawny buff, broadly barred with brown. Underwing coverts tawny buff, barred with brown.

Immature and juvenile: Similar to adult, but upperparts and wing coverts sprinkled with brownish white feathers, boldly spotted tawny wth blackish brown tips. Scapulars and tertials brownish white or frosty white, vermiculated with brown and boldly spotted with blackish brown and tawny. Primaries broadly tipped with brownish white mottled brown, and the rectrices narrowly tipped with grayish brown mottled brown.

There is no information available on molts of Rufous-bellied Nighthawk; presumably this species follows the complex basic molt strategy.

Iris: dark brown

Bill: blackish

Tarsi and toes: brownish

Bare parts color data from Cleere (1998).

Total length: 23 cm (Ridgely and Greenfield 2001b), 23-25 cm (Hilty 2003)

Linear measurements (from Cleere 1998; n = 5 or more):

male

wing length (flat): range 208-219 mm

tail length: 83-85 mm

bill length (from base): 13.2-15.5 mm

tarsus length: 14.0-16.2 mm

female

wing length (flat): 205-210 mm

tail length: 80-84 mm

bill length (from base): 13.2-15.5 mm

tarsus length: 14.0-16.2 mm

Mass: no data?