Short-tailed Swift
Chaetura brachyura
The short-tailed swift is about 10.5 cm long, and weighs 20 g. It has long narrow wings, a robust body and a short tail. The sexes are similar. It is mainly black with a pale rump and tail. It can be distinguished from related species in its range, such as the band-rumped swift (C. spinicauda) or the gray-rumped swift (C. cinereiventris) by the lack of contrast between the rump and the tail, the latter being much darker in the other species.
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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