Do you have a secure run for them? (with a skirt around the base, at least bird netting over the top?) Even that is not secure if it's made of chicken wire. But, that's what I have, b/c that's what I can afford. That will afford some protection during the day. The only way you can try to keep them safe if you let them out to free range is to sit outside with them and hold a shot gun. I let my birds out to range some times, but not every day, and not all day long. It all depends on what's going on. If hawks seem to be more vocal, present, I will keep them in unless I can be out with them. If coyotes are singing in the morning, or have been singing a lot at night, I am less likely to let them out.
Keeping chickens is risky business, whether you keep them shut in a run or let them free range. One could argue that they are more at risk in a run, cause a predator could break in, and then your birds would be trapped in the run WITH the predator. Kind of like catching fish in a gold fish bowl. Outside the run, at least they could run, and perhaps hide, depending on the landscaping in your yard.
Most important is that you keep them shut in a safe coop all night, every night. If your coop has an opening that you could push a quarter through, a weasel can get in, and he'll kill an entire flock in a single night just for the thrill.
