It can help to keep a fierce rooster
So if you keep your birds enclosed, do make sure it is absolutely secure against predators. Predators can dig under, go over and in some cases go through, if you've made the mistake of using chicken wire for your run. Remember, chicken wire is not secure against determined predators--it will keep chickens in, but it won't keep predators out.
If you are looking for a breed that is quick enough to escape predator attacks in a free range situation, you will probably be looking for a smaller "flighty" chicken breed like a Hamburg, Leghorn, Campine, Ancona or various game bantams.