We live right in the middle of a residential neighborhood and plan to keep 15 hens, consisting of Black Australorp, Buff Orpington, Barred Rock, and Rhode Island Red birds. We plan to let them use the entire back yard as a run on the days they are let out. It measures approximately 75' x 65' and it has a 4' fence surrounding the entire area. With the size of the yard, plenty of water and feed, etc., would these size birds be apt to fly out? Given their large size, will they even be able to fly that high? Just trying to get my thoughts together before they are grown and allowed out in the yard.