I dont use hay anymore as they scratch it out as they are settling their fluffy butts down. The bottom of my next box is wooden, so I had found some eggs with a tiny crack in the past. Now I use wood shavings or sawdust, and have it 2 or 3 inches deep so even when they nest and dig they cant get down to the bottom, and lay their eggs on the nice cushy shavings. No more cracked eggs.