you can lay down sand, shavings, straw or hay. the bare ground in the outside run isn't all bad either-great for dust baths! the inside however should have some kind of bedding or you will risk bumble foot (an infection in the pad of the foot of poultry caused by stappholcaucus aureus in the manure which penetrates the foot through cuts in the skin) when your birds jump off the roost onto the wire floor.