i freerange my chickens and guineas and have had a few losses. i am right on the edge of a heavily urbanized area and hundreds of acres of wooded gvot land. i have seen one stray dog and several hawks take mostly adolescent birds. the other problem i have is that i have so many snakes around my wooded acreage. i caught one snake with 6 ingested egg "lumps". i dont kill the snakes, but have hauled the biggest ones off ...on a few occasions.
my great danes and rat terriers make great flock watchers for the most part. i have an open air coop too. i have a covered roof, but all sides are 1"x2" galvanized wire. the dogs and chickens get along very well. i give them alot of credit!