Chestnut-collared Swift
Streptoprocne rutila
The chesnut-collared swift is one of the smaller members of genus Streptoprocne. It is 12 to 14 cm (4.7 to 5.5 in) long and weighs about 21 g (0.74 oz). It has a wide slightly notched tail and broad wings. Adult males of the nominate subspecies S. r. rutila have a sooty blackish brown crown, a blackish brown back, slightly paler rump and uppertail coverts, and a sooty blackish brown tail. They have a narrow black patch around the eye and grayish brown cheeks, chin, and throat with some dull rufous feathers mixed in. Voice: One description of the chesnut-collared swift's flight call is "buzzy...like electric crackles or static, occasionally strung into a chatter: bzzzz'tzz'tzz'tzz zz zzzz zzzzz zzzz."
ID text from Wikipedia, CC BY-SA 4.0
White-collared Swift
Streptoprocne zonaris
The white-collared swift is the largest species of swift in its range except in northwestern Mexico, where it and the slightly larger white-naped swift (S. semicollaris) are sympatric. The white-collared swift is 20 to 21.5 cm (7.9 to 8.5 in) long and weighs 90 to 125 g (3.2 to 4.4 oz). It has a wingspan of 45 to 55 cm (18 to 22 in). It has a very slightly forked tail and the sexes have the same plumage. Adults have a white collar that circles the neck and is broadest on the breast.
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: Chestnut-collared Swift and White-collared Swift.