Uncommon swift found along the east slope of the Andes from central Bolivia to northwestern Argentina. Uniform sooty brown, lacking any strong plumage characteristics. Easily confused with Sick’s Swift, but is larger with longer wings, giving it a sleeker and more aerodynamic appearance; also lacks a pale throat, though this is often hard to see clearly. In central Bolivia it could be mistaken for Chestnut-collared Swift (some of which lack a chestnut collar), but wings are slightly narrower at the base. Usually seen in flocks of a few birds up to 20 or more that circle over humid forest.