You will occasionally hear that barn owl boxes need no bedding—that they use their own pellets for bedding. But this will not be enough to cover the floor by the time the eggs are laid. Always place 3-4 inches of garden mulch across the entire floor. This mulch should not be shredded, but be large pieced. Bark mulch made from pine, fir, or hardwood is best. Ace Hardware sells a product called Western Bark Mulch which is ideal.