For a pair of them, I would say 1x1, 1x2 for a trio and so on. However, Coturnix do best when kept in colonies, as the females get pretty roughed up. Not to say that it can't be done succesfully, as this is how I do it part of the year, but just a warning! ^_^
I've not got any yet, but are quail really that small that you can put so many in a 4x4 ? just wondering because I have 2 coops of similar size and was thinking less birds would go in.
NO THEY ARE NOT THAT SMALL. AND IN MANY CASES WILL TOLERATE OVERCROWDING LIKE THAT.... IT REALLY DEPENDS ON THE INDIVIDUAL BIRDS THEMSELVES. ALSO CHECK WITH YOUR LOCAL FISH AND GAME DEPT AS THEY MAY HAVE MINIMUM SQ/FT PER BIRD RULES--- SOME STATES DO, MANY DO NOT