Nightjars are nocturnal birds with plumage that is cryptically patterned, and dominated by shades of brown. They have long wings, short tarsi, very wide but short bills, and prominent rictal bristles. Yucatan Nightjar is a medium sized, relatively dark nightjar. The upperparts are cryptically mottled with brown, black, and gray; the most prominent feature is a tawny or buff collar across the hind neck. The wings are entirely dark, with no white or buff band across the primaries. The underparts are mottled with blackish, brown, and white, with a relatively broad white collar on the lower throat. The sexes differ in tail pattern: the male has very broad white tips to the outer rectrices, but these tips are narrower in females, and are buffy white.
Yucatan Nightjar broadly overlaps with Common Pauraque (Nyctidromus albicollis), but the pauraque lacks the tawny nuchal collar, has rufous auriculars, and has a white (male) or buff (female) band across the primaries; male pauraque also has much more white in the tail. Chuck-will's-widow (Antrostomus carolinensis) and Mexican Whip-poor-will (Antrostomus arizonae) lack the tawny nuchal collar; Chuck-will's-widow also is larger and tawnier. The allopatric Tawny-collared Nightjar (Antrostomus salvini) is very similar to Yucatan Nightjar, but has smaller white tips to the rectrices, and a less prominent white throat band; these two species also have different vocalizations.
The following description is based on Cleere (1998); see also Ridgway (1914):
Adult male: Forecrown, crown, and nape grayish brown, speckled and spotted with grayish white, boldly spotted with blackish brown. There is a broad tawny or tawny buff collar across the nape and sides of the neck. The back, rump, and uppertail coverts are grayish brown, speckled with buff and cinnamon, broadly streaked with blackish brown. The scapulars are grayish brown, heavily speckled with pale buff, grayish white, and cinnamon, with large irregularly shaped blackish brown spot. Rectrices brown, faintly barred with tawny. The three outermost pairs of rectrices are broadly tipped with white (white band ca 45 mm in extent); the pair inner to these (R2) is narrowly tipped with white (white band ca 8 mm in extent), especially on the outer webs; and the central pair of rectrices (R1) are broadly tipped with grayish brown mottling. The wing coverts are grayish brown, finely speckled with cinnamon, pale tawny, and grayish white, and spotted with buffish white or cinnamon. Primaries are brown, spotted on the outer webs and faintly barred on the inner webs with tawny. Secondaries brown, mottled with pale tawny and pale cinnamon. Lores and auriculars tawny, speckled with blackish brown. Chin and throat dark brown, narrowly barred with cinnamon. There is a broad white band across the lower throat, bordered below by a broad buff collar The breast is brown, speckled with pale buff and cinnamon, and heavily spotted with white. Belly and flanks blackish brown, speckled with cinnamon and barred with brown, boldly spotted with white. Undertail coverts bufff or buff barred with brown.
Adult female: Similar to the adult male, but the pale tips of the outer rectrices are much reduced in size (ca 10 mm in extent), and are buff, not white.
There is no information available on molts of Yucatan Nightjar; presumably this species follows the complex basic molt strategy.
Iris: dark brown
Tarsi and toes: blackish brown
Bare parts color data from Cleere (1998).
Total length: 24-25.5 cm (Howell and Webb 1995), 25-25.5 cm (Cleere 1998)
Linear measurements (from Cleere 1998):
male (n = ?)
wing length 167-172 mm
tail length 120-128 mm
bill length 17.4-18.1 mm
tarsus length ca 18 mm
female (n = ?)
wing length 167-174 mm
tail length 112-125 mm
bill length 16.6-18.3 mm
tarsus length 18.0-18.2 mm
Mass: male, 65.5 g (n = 1; Paynter 1955); female, 51.2 g, 55.7, 64.3 g (Paynter 1955, Russell 1964, Cleere 1998)