Sometimes in pairs, sometimes in small coveys. Most examples of domestic coturnix roos are too aggressive as breeders to be left in a pair. Most likely because they have been bred in captivity with no oversight for over a thousand years. Some things I've read suggest coturnix were even domesticated before chickens. Domestic cots can't survive outside their cages because they lack so many wild instincts. In fact I've only ever seen proof of two examples of a domestic coturnix hatching it's own eggs. They won't flee predators, they've been bred too heavy for good flight, and as mentioned cannot raise their own young.
If people continue to breed CBBQ the way they are now, they too will end up as "dumbed down" as coturnix. Buttons that will brood their eggs are becoming more rare already, and most examples of the wild color are already too impure to bred true to color.