I need to build a couple of maternity pens, how big do they need to be? They will brood in there, and raise their chicks in it until the chicks are big enough to mix with the main flock. I expect most of the broody hens to be bantams. They will probably have anywhere from 1 or 2 chicks to, say, a dozen. Standard and bantam chicks. I do have some "scrap" rabbit cages, they are 3' x 30" x 18" H. Would these be big enough? They are too rusty to keep rabbits in, but should work just fine for chickens.