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.
Are you planning to travel to Iguazu Falls?
Or travelling to other parts of Brazil, Argentine or Paraguay.
First! Check your papers and the requirements for it country.
This post can help you to find the links with all the informations …