I've had mink attack in broad daylight running through the long grass right past me. Also had hawks and an injured owl attack while I was standing right there. I've also had owls do very scary "fly-bys" at my Pomeranian dog at night! That was really, really creepy as you could feel the air displaced by the wings.
All that being said, we still have free-range animals. Yes, every year we lose one or two but the trade off of having a thriving, happy yard is worth it, imo. There's definitely a learning curve to hunting the hunters--the first year we lost 14 chickens before we finally nailed the culprit. And there are laws, you can't shoot an owl, for example (but fortunately in my area, the owls only pass thru for a short period of time--so now we know when to step up other security measures). Most importantly, a secure roost at night and do not let your birds out until the sun is high in the sky. Keep a good rooster, he's worth his weight in gold as he'll always be watching and will sound the alarm before running for shelter himself. A few good battle-axe hens will do the same, keeping the youngsters safe in a daylight attack. Provide run-in shelters and keep the grass low. Weasels and mink will attack from a tuft of grass but will not like to be running across a trim lawn.
The birds who survive will learn from the loss and grow stronger. And a good rifle helps, too.