Nightjars are nocturnal birds with plumage that is cryptically patterned, and is dominated by shades of brown. They have long wings, short tarsi, very wide but short bills, and prominent rictal bristles. Buff-collared Nightjar is a medium sized species of nightjar, with generally grayish plumage. Both sexes of Buff-collared Nightjar have a narrow rufous collar across the nape, and the primaries are primarily dark (lacking a white band across the primaries, as is present in many other species of nightjar). The three outermost pairs of rectrices of the male are prominently tipped with white; the tips of the rectrices of the female are pale cinnamon or whitish.
Buff-collared Nightjar is most similar to Mexican Whip-poor-will (Antrostomus arizonae) and to Eastern Whip-poor-will (Antrostomus vociferus), but the whip-poor-wills are larger, darker in color, lack the rufous nape collar, and have different songs. Common Poorwill (Phalaenoptilus nuttallii) is smaller, shorter tailed, lacks the rufous nape collar, and has a very different song. Eared Poorwill (Nyctiphrynus mcleodii) is browner, is boldly spotted above, lacks the rufous nape collar, and has a different song. Common Pauraque (Nyctidromus albicollis) is larger and longer tailed, has rufous sides to the face, lacks the rufous nape collar, has a white or buff patch on the wing, and the male has much more white in the tail.
The following description is based on Ridgway (1914) and on Cleere (1998):
Adult male: Forecrown, crown, and nape grayish brown, narrowly streaked with blackish brown. Lores and auriculars brown, speckled with buffish. Broad tawny or cinnamon buff collar across hindneck. Back, rump, and uppertail coverts grayish brown, streaked with blackish brown, and faintly barred brown. Rectrices brown, broadly barred with grayish brown and with pale tawny buff mottling. The three outer rectrices with broad white tips: these white tips broadest on the outermost rectrix (with a length of 40-58 mm) and narrower on the inner rectrices, and the white almost confined to the inner webs on Rectrix 3. Wing coverts grayish brwon with irregularly shaped blackish brown centers, and speckled and spotted with grayish buff and buff. Primary coverts brown, barred or spotted with tawny. Primaries and secondaries brown, regularly barred and spotted with tawny, and tipped with grayish brown mottling. Tertials grayish brown mottled with brown and buff. Chin and upper throat grayish brown, speckled with brown. Lower throat buffish white, forming a band that is continuous with the tawny collar on hindneck. Breast grayish brown, tinged with cinnamon, and streaked and speckled with brown. Belly, flanks, and undertail coverts pale buff, barred with brown.
Adult female: Similar to adult male, but the tips to the outer rectrices are buffish and are narrower (ca 12 mm in length).
Immature: Similar to adult, although some retain juvenile secondaries, which are more heavily tippped with buff or cinnamon. The outer rectrices of immature males are tipped with buffish white, and the pale tipping is less extensive than in adult males.
There is little information regarding molt of Buff-collared Nightjar; see Pyle (1997). The First Prebasic Molt is partial, and probably includes a variable number of wing coverts. The second and subsequent Prebasic Molts also can be incomplete, with some secondaries and, less frequently, some primaries and primary coverts retained. There is no Prealternate Molt.
Bill: brown or blackish
Tarsi and toes: black or brownish
Bare parts color data from Cleere (1998).
Total length: 21.5-23 cm (Howell and Webb 1995), 21.5-24.5 cm (Cleere 1998)
Linear measurements (from Cleere 1998):
male (n not specified, but a minimum of 5)
wing length, range 146-161 mm
tail length, range 106-125 mm
bill length, range 15.7-17.4 mm
tarsus length, range 17.0-19.8 mm
female (n not specified, but a minimum of 5)
wing length, range 155-162 mm
tail length, range 110-121 mm
bill length, range 14.6-15.0 mm
tarsus length, range 15.0-19.4 mm (n = 3)
Mass: male, range 44.7-53.7 (n = ?; Cleere 1998); female, range 45.0-52.8 g (n = ?; Cleere 1998); mean 48.0 g (range 39.8-61.0 g, n = 6, Mexico, sex?; Dunning 1993).