It is a risk tolerance issue. We have a pretty secure run. No losses in it in 3 1/2 years. We also have a fenced area that is just 2'x4" welded wire. No cover. We lost three 8 week chicks this summer. Half of our new birds. We were in the yard most of the day and did not witness it. Never found the culprit. I suspect a weasel or hawk. After keeping all birds in the secure run for two months we just started letting them out again. Fingers crossed that as they are now full grown they will escape all but the worst attacks.