The Great Dusky Swifts do not perch on branches or on the ground, but they can be seen on the rocky vertical walls, which they catch on to by their nails. They build their nests behind the falls by sticking them with saliva on cavities or projections of rocky walls, this way they are protected from predators. During the day you can see flocks of up to 3,000 swooshing through the falls so gracefully.
