I free range my Muscovy's, alot of my chickens, peacocks, guineas and I live in the heart of predator country. What I've found is that 99.999% of our predators come out at dawn, dusk, or during the night. So those are the times that our poultry aren't free ranged.
I would suggest that before you free range to know your area.
What are the dangers to your birds?
Are there fliers? (hawks, eagles? etc?)
Are there ground critters? (raccoons, possums, bobcats, coyotes, dogs)
What are their hunting patterns?
What is the area around you like?
Are there lots of predators around you at a specific time?
Will you be around while your poultry is free ranging?
There are a ton of other questions but these are basic ones. In 3 years we have only lost one free ranged rooster. But this past year we were hit by predators hard at night that went after our penned birds and we lost a bunch of birds. None of them were the free rangers. Weird.
Anyway, free ranging really does wonders with eggs. And I love watching my birds wander my property.