This is why we built a huge fenced in run for our chickies. We have all kinds of predators, and in our fields ravens, owls, and raptors are out hunting in our fields for any the small animals my cats don't catch. There is just no way we'd let them free range, but I hope we have given them enough space to do some forage. The coop is under a canopy of large 40-60ft maple trees so the run is covered. The birds don't seem to see them under that, but there are still foxes, coyotes, and even one of our own cats (the only loss we've was because of her) on the ground.
Maybe in future years, it won't be as upsetting to lose one (or more) and we'll let them roam (we keep that particular cat in the house while the chickies are in their run), but for now I feel like I made a personal promise to care for them and allowing them to fall prey to the food chain earlier than necessary makes no sense to me.
Good luck to you.