Chuck-will's-widow
Antrostomus carolinensis
The chuck-will's-widow has a short bill and a long tail typical of the nightjars. It has mottled brownish underparts, a buff throat, reddish-brown feathers lined with black, and brown and white patterning on head and chest. Males have patches of white on their outer tail feathers. It is the largest nightjar in North America. In length, it ranges from 28 to 33 cm (11 to 13 in). The wingspan can range from 58 to 66 cm (23 to 26 in). The body mass of the species is from 66 to 188 g (2.3 to 6.6 oz). Among standard measurements, the wing chord is 20.1 to 22.5 cm (7.9 to 8.
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: Chuck-will's-widow and Mexican Whip-poor-will.