The Great Dusky Swift is found in central, eastern and southern Brazil, eastern Paraguay, northern Argentina and north-eastern Bolivia.

It nests and roosts at waterfalls while feeding over the surrounding countryside. For this reason it is highly localised though common where it occurs.

It is a large swift, brown in colour with a pale head and slightly pale rump. It has long, broad wings and a squarish or rounded tail.

These photos were taken at the marvelously named Cachoeira da Pancada Grande or "Waterfall of the Big Thump" which is outside the distribution range normally shown.

There is a distribution map from NatureServe and additional information available via Avibase. There is also a page on Wikiaves.