While not forbidden by law, the mixing of bird species with different adult sizes has it's definite hazards. As many poultry enthusiasts have learned that chickens possess the innate instinct to brutalize, maim, kill and/or devour anything that is significantly smaller than themselves. Given that adult Jumbo Coturnix are around 1/3 the size of an average Bantam and 1/8 the size of a standard Plymouth Rock, it would be inadvisable to house quail with chickens due to the inherent physical dangers.
Chicken wire enclosures suitable for containing large poultry have openings that allow a quail to put it's tiny head through the wire mesh. This would allow a predator to bite the heads off your quail. It is recommended by many that quail be kept in pens that are protected by 1/2" x 1/2" wire mesh to prevent this situation from occurring.
Additionally many chickens carry diseases that are fatal to quail. Even though your chickens do not appear to be sick they may possess within their bodies or feces illnesses that will decimate your quail population. It is true that some folk allow quail to mix with their chickens, but many others feel it is akin to playing Russian roulette, you may win or your quail may die a horrible painful drawn out death. You've got to ask yourself a question: Do you feel lucky?
Lastly quail, being game birds, require a different diet that chickens. Quail should be fed a special game bird diet that is 24 - 30% protein, higher is better. Chicken feed is significantly lower in protein than is required to provide a quail with complete nutrition.
Please do not let any of this dissuade you from raising quail. Many quail fanciers raise other species of birds but they normally separate each species into different pens, feed each a specific diet and thoroughly wash their hands in between visits to each enclosure.
