Having a truly predator proof coop, and hopefully a run, will greatly improve your bird's safety. Many of us have learned the hard way that our coop and/ or run aren't safe enough, so start there with serious security.
Free ranging is a risk everywhere, if you are present or not. A hawk will take one bird at a time, maybe every three days or so, if you don't lock the flock in after that first attack. Better than any canine, who will try to kill every bird out there all at once! Weasels and raccoons are most dangerous at night when the birds are roosting, when either will kill the entire flock in a short time.
This year we aren't free ranging because of avian influenza, otherwise our birds are out nearly every day, and we have had losses, sometimes one to a hawk, three times multiples to a fox and a dog.
Have a large enough safe place for your birds for the weeks when they may be locked in, don't depend on free range time as reliable extra space.
Mary