Adults have a chocolate brown crown and throat with pale gray edges to the feathers, giving a frosted appearance to the face.

[6] The great dusky swift is found in Brazil from southern Pará and much of Mato Grosso east into Bahia and south to Rio Grande do Sul, in eastern Paraguay, and in northeastern Argentina's Misiones Province.

The species roosts around waterfalls and is known for flying through the Iguazu Falls on the border of Brazil and Argentina.

[6] The great dusky swift nests in large colonies on a cliff, either beside or behind a waterfall.

The great dusky swift's principal vocalization is described as "a ti-ti-ti sound followed by a buzz, tirr-tshaarr.