I agree with BoltonChicken about the clod of dirt. My coming 3 week mixed batch were getting bored even with their bigger space and rocks and sticks etc (with dirt on them as they came from the garden) so I tried his suggestion of bringing in a clod of dirt and grass. I put it all into a big chefs baking pan, dampened it a bit and they had a great time wearing themselves out fighting over treasures climbing on and jumping off, getting to really scratch for something. So until I can get the real pen and coop done, over the next 3 weeks, they can enjoy their indoor playpen, about 5' by 5' though they are now threatening to fly over to me when I come into the room!