Dusting is done by many meadow birds, like larks, sparrows, wrens, and owls. Dusting is when one of these birds finds a dusty hollow, and fluffs around in it, rolling in it. Once they have lots of dust on them, they shake and flap to remove it again.
Scientists are unsure exactly why birds do this dusting, but most feel that it is a way to remove excess oils from their wings. It also helps get rid of bird lice and other small pests. It is not simply another way of bathing - many birds bathe in water, but also dust themselves.