I have a flock of free rangers that sleep/roost in a tree that's lit up by my big yard light... from 32 adults I am down to 12, their numbers have dwindled that much in the past 4 years. Over those last 4 years the others have become a little more "street smart" from watching their siblings and mates get taken by predators, and they usually switch roosting trees after one is plucked from the trees. I have a donkey, 7 horses, 17 goats, 5 dogs and my 10+ acres is now well fenced and cross fenced (for goats). Great horned Owls are their worst predator now that the ground predators are kept out for the most part. They owls also took out 2 of my Turkeys. The rest of my (breeding) flocks stay cooped until mid or late afternoon after all the Hens have laid their eggs for the day, then they get to free range in the afternoons, supervised. My breeding flocks are too valuable to me to feed predators with my fancy colored birds (that I have bred most of myself). BUT, I am tick free, so are my animals... and the rattle snakes and spiders are under control too. Everyone has a different set up, different trees, different predator load, different birds... but realistically there aren't that many full time free range flocks that can sustain themselves on their own.