I'm drawing up some sketches for a coop and want to put a kind of "mini" run at the bottom (so that the coop is on top, but they can go down the ladder into the fenced in area at the bottom) so that they can still peck around if I have to put them up while I'm away from the house (I plan to let them free-range around the yard as long as we are home). Anyhow, I'm trying to figure out how "tall" the average standard chicken is (not bantams and not something large like a Jersey Giant). I'm thinking of something like an Australorp, RIR, etc. I need to know this to build the "mini" run at the bottom of the cage. Thanks.