I also disagree with Baby Newbird. I have 2 mountain quail 2 gambles quail and a bobwhite in a community aviary with my diamonds. They are in a 8x8x7 outdoor aviary. I started out with four birds (pairs sell for $20 around here) I now have seven due to a very productive pair who have had two nests in less than 2 months. They were starting a new one but the storm we had the last two weeks blew the rain into the aviary and soaked the nests. The baby doves will actually nestle up against the quail if they get the chance because the quail like to try to roost on the same poles the doves do.
The only bird that did not work in this aviary were a few parakeets I rescued. Whenever the quail would panic (like when a hawk decides to sit on the corner of the aviary and tries to get in.) the quail would accidentally run into the parakeets and get them agitated and I caught the male parakeets trying to bite the baby doves. I got rid of them before we had a real incident besides loosing a few feathers and so far the pairing of the quail and doves has worked nicely.
There is nothing funnier then seeing my quail walk around with doves on their back, which is a recent thing they have been allowing the doves to do. The doves will fly up when they get scared and will just land wherever they end up which lately has been on a quail. Both birds will also sit in the same feeder bowl and eat at the same time without any problems.
If you provide each bird with enough room to have its own space you shouldn't have problems. Community aviaries are a common thing here, I knew a guy that had 4 types of pheasant 5 types of quail, chukars, doves, guineas, finches, and wood and mandarin ducks all in one huge aviary. He probably had about a hundred birds. I think the aviary was roughly 30x 60 or less, but all the birds got along. I would have thought there would have been a lot of feather plucking and fighting, but all the birds seemed to do fine. (edited to say I got my doves from this guy but he also had normal sized doves as well)
My website has pictures of my birds, and I think both types of birds in a few of them