Grey-rumped Swift
Chaetura cinereiventris
The grey-rumped swift is about 10.5 cm (4.1 in) long and weighs about 17 g (0.60 oz). It has a protruding head, a short square tail, and wings that bulge in the middle and somewhat hook at the end. The sexes are alike. Adults of the nominate subspecies have mostly glossy black upperparts with a wide gray rump and uppertail coverts. Their underparts are a lighter gray than the rump, though darker on the undertail coverts. Juveniles are essentially the same as adults with the addition of pale fringes to many of the wing feathers. Subspecies C. c. Voice: The principal vocalizations of the grey-rumped swift's nominate subspecies are "a bright repeated short 'tsip'" and a "series of 3–4 slightly downslurred burry drawn-out notes 'trrreeew-trrreeew-trrreeew'." The other subspecies' vocalizations vary but are similar to them.
ID text from Wikipedia, CC BY-SA 4.0
Sick's Swift
Chaetura meridionalis
The upperparts dark smoky brown. The tail is ashy grey with dark shafts and protruding spines, The throat is grey, lower underparts dark brown, bill and legs black.
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: Grey-rumped Swift and Sick's Swift.