The gestures that birds make when they put dust on their feathers and then shake and preen it off look like the movements they make when bathing in water, but the purpose is not exactly the same.
Birds take dust baths to rid themselves of all sorts of parasites that crawl in and between their feathers.
Lice and mites are common to birds and infest them in great numbers, particularly birds away from water, like quail and others that live in relatively dry areas.
For birds, taking a dust bath is much like rubbing your hands with sand to get grit and grime off.
The abrasive dust helps the birds remove parasites.
Some authorities have suggested that the purpose might be to keep the birds’ plumage fluffy by removing excess moisture and oil, but others say there is no convincing evidence to support that theory.