Weasels are terrible critters. They will get in your hen house and kill all of your birds just for fun. They don't eat them. The worst part about them is they can get through very small holes in fencing, so are hard to keep at bay.
have large numbers of bald eagles around my place. You can tell when one is coming. All the hens start heading for cover, seemingly for no reason, then a few seconds later the eagle will pass overhead. They have never bothered my hens, but I think they are just keeping them around in case all other sources of food become scarce.
PS. Bald eagles are snake catching machines.