There is something about doorways that invite chickens to dust bathe. I read about it in the chicken books before having chickens, and my hens definitely display the behavior. Maybe because the area gets frequently trod upon, the dust is finer and in greater quantity? Well, in greater quantity until the chickens get to it. It is amazing how much dust collects in their feathers. Ha. People have known of this bit of poultry magic for over a century, hence the use of feather dusters. By the way, there seems to have been a bit of drama in the patent process of the feather duster. Susan Hibbard, who was ultimately awarded the patent, had to fight her husband who claimed the idea was his own. If you want to follow me down the feather duster rabbit hole, here is a place to get started. I was quite surprised that feather dusters are not that old, then read that people would use whole wings to dust the hearth, but had to keep the necrotic tool from the teeth of the cats and dogs. So it is the tying of the feathers to a stick that was the patent able invention. But you still have to keep it out of reach of the cat.