On a sunny day, chickens enjoy taking dust and dirt baths. They can really kick up a storm, turning upside down even to work dust and dirt deep into their feathers and onto their skin. They do this to clean themselves, and to get rid of parasites. How this works is that the dust clogs the breathing pores of the parasites, killing them. Smart birds.
That’s why when chickens shake their bodies, sometimes they leave behind a cloud of dust.