Its a general guideline (lemme stress GENERAL and GUIDLINE) 1sq ft per bird for COTURNIX quail. As mentioned earlier bobs/ valleys/ gambels/ mtns will roost. coturnix and buttons generally do not. Coturnix as usually do better in a pen with less flight space.... It makes them injuring themselves harder if they dont have enough room to flush and bounce off the ceiling... Also do not use the 1/4 in hardware cloth as a bottom-- the feces will not fall thru and thereby make you the official poop scooper while trying to retain your birds.