I have a Buff Orpington, and he does a great job alerting the hens AND me to any danger at all. Cats, hawks, noises that he doesn't know are safe, unwanted people (um, well, I welcome them but he won't allow them in the pen at all). I can't free range mine, we have way too many hawks/owls and other predators that are a danger to them. I have a large round pen with wire across the top, but he still alerts. I've been working hard to learn his calls (regular egg song, regular crow, distress song, distress crow, little squabble noises he makes, etc), watching the hens react helps to learn them quicker for me too.