Try with mixed age and sex flocks with birds with more substance.This has not been my experience. There is heavy hawk predation in my area. Several summers ago, I lost 3 full grown birds to Northern Goshawk. This prompted me to change up my management style. My flock is now penned in a covered run unless I can be out and about to protect them. When I let them out to free range, hawks often show up within 10 minutes. They are brazen, and will sit in trees and taunt me. They will hang out on the run, trying to figure out how to get into the run, and I've seen a hawk on ground casing out the cockerels in the grow out pen. My neighbor has perfect cover for his flock: pasture with heavy weed and shrub cover. Yet, he has lost a number of full grown birds to red tails. He has also had to keep his flock penned unless he sits vigil to guard them.