Great Dusky Swift are found at big area in eastern of South America Bolivia, Brazil, Paraguay, and Argentina. It clings to exposed rock faces near or behind the waterfalls, where they breed and nest. The flight (dance) around the falls make the scenary even more beautiful , you can see the swifts crossing the cascates through the water.
They are in abundant number at the Iguassu Falls where they breed and nest. They Breeds in colonies, near or even behind waterfalls. Unlike other species the Great Dusky Swift also breeds in direct sunlight. The nest is a disc-shaped conem made of moss and pebbles, hold together with mud.
They feed in the flight over the forest canopy, taken insects in the air.
Great Dusky Swift is dark grayish brown with a silvery head, and is fairly large in size.