Buff-collared Nightjar
Antrostomus ridgwayi
The buff-collared nightjar is 22 to 23 cm (8.7 to 9.1 in) long. "A. r. ridgwayi" weigh 39.8 to 61.0 g (1.4 to 2.2 oz); one male A. r. troglodytes weighed 51.0 g (1.8 oz). The head, upperparts, and tail are brownish gray with gray, cream, and rust markings. It has a bright cinnamon buff collar on the hindneck and a narrow buffy white band under the throat. The wings are brownish black with cinnamon buff bands. The breast is brownish gray and the belly tan with dark brown bars. The ends of the two outermost tail feathers have much white in the male and a small amount of buff in the female. Voice: The male buff-collared nightjar's song is a "long rising, accelerating series of cuk notes ending in cuk-a-cheea that drops suddenly at the end." Both sexes make "chuck" calls; males give a "quirr" call. It typically sings the most at dawn and dusk but will continue intermittently through the night. It sings nightly between mid May and early August and infrequently during the rest of the year.
ID text from Wikipedia, CC BY-SA 4.0

Mexican Whip-poor-will
Antrostomus arizonae
The Mexican whip-poor-will is 23 to 24 cm (9.1 to 9.4 in) long and weighs 45 to 50 g (1.6 to 1.8 oz). In general its upperparts are grayish brown with blackish brown streaks; the crown has wide blackish brown stripes. The throat and breast are blackish with a thin white band on the lower throat between them. The belly is buff with brown bars. The male's outermost three pairs of tail feathers have broad white tips; the female's are narrower and buffy. The wings are brown with tawny and buff spots and speckles. The subspecies differ somewhat. Voice: The Mexican whip-poor-will is more often heard than seen. Its song is an onomatopoeic whip-poor-will like that of its eastern congener, but lower in pitch and "less 'snappy' and slightly 'lazier'". It also makes a variety of other sounds including "a single, low, mellow quirt or queerp note", a growl, and a "growl-chuck".
ID text from Wikipedia, CC BY-SA 4.0

Where you might meet both
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Play today's Daily BirdPhotos and recordings are credited to their authors under the licence shown. Full profiles: Buff-collared Nightjar and Mexican Whip-poor-will.