I'm not sure of the size of your small back yard. If you just want to be sure to keep chickens in (and hawks out) I recommend aviary netting to cover the back yard. Aviary netting (about $50 for 50' by 50' piece, Amazon) keeps your birds safe from hawks and will completely prevent escapes (some do manage to fly over even a 6' fence). I installed it to protect my ducks from hawks. (It does not protect against raccoons and things that can chew through it; my dog protects against those dangers since they can run around the coop and pens.) The netting can be held up by a PVC pipe framework or any other simple framework, or even wires strung between trees. This may or may not be what you need, but it does work well to keep birds in. It is also very lightweight and sturdy.