How close can my quail breeders be to my chickens?
A Good rule of thumb is TEN MILES. I lost 450 Bobwhites, last year, because a hired "hand" (more like hired two left feet, not connected with a brain) went from chicken house, to Quail pen, after being told it was better to let the chickens starve, than to do that.
Some companies that let contracts for broiler chickens demand a barrier of 100 feet. Others will not allow any other birds (chickens, waterfowl, gamebirds, or guineas) on the same property. I would say 50 to 100 feet would be OK,
IF you drag your feet through tall grass, as you walk. Boot baths at the entrance to each pen, helps. Having the Quail on wire would help, but do not ever put an escapee back in, if it could have gotten to chicken poop. Airborne spreading of diseases is probably not likely, but some can be spread by flies, and Mosquito's. Do not allow use of waterers, or feeders from pen to pen. Use slightly different, or marked equipment.
Some people have raised them together and claim to have had no problems. Some people wouldn't have any idea what killed their birds, so there may be some overlap in these groups. I was lucky for a long time, myself. A hot, wet summer may be your worst enemy as far as diseases. Second is damp conditions at any temperature. Third is a helper with no stake in the success of the bird crop.