If you have hens, that will be big reason number one for not running away. Reason number two, make sure to still throw them some food or treats so they know where they get there meals.
How big is your yard?
You can always limit the amount of time they stay out. I let my flock out just a couple hours before sundown. This keeps them near their roost/coop and easier to round up and lock up.
As for hawks, the only way to truly avoid them is to keep your birds covered at all times. If you let your birds out of their covered run, they are at risk. Providing things to duck under will help minimize a successful hawk-attack. They will naturally watch for hawks, sometimes it even takes witnessing one hawk attack to learn to keep an eye on the sky. If you let them free-range you will have to accept you are opening your birds for an attack.
Cats are usually not a problem. Coons and possums are normally nocturnal, so if you lock your roosters back up at night they'll be much safer. Daytime predators to watch for are mainly hawks and dogs.
Free-range predations are cut down significantly by securing the birds at night, because the majority of chicken-predators are nocturnal.
I free range my extra roosters. Anything I depend solely on for breeding stays locked up in their run, due to Murphy's law. With my luck a hawk would decide to eat all my valuable birds and leave the rest. I've noticed my roosters are much, much more predator wary than my hens.
-Kim
