I have had border collies, jack russells and a black lab around my chickens. The black lab would retreive the chicks and drop them on our porch, only he would usually retreive them too hard and they would have puncture wounds, or be dead. We had to get rid of him, he would not only harm the babies but he would chase the full grown chickens and pull their tail feathers out. The Jack Russell I had then was fine with them, but she was really just a puppy. I still have her and love her to death so I hope she gets along well with the chickens. The border collies try to herd the chickens which the chickens don't like, so the BCs usually just end up chasing them, but not otherwise harming them. I have heard that Great Pyreneses are great poultry gaurdians from people on the web and also my friends neighbor has one and he says she is great (he don't treat her very good though GRRR, not really abuse just doesn't feed her very well, doesn't worm her often (if at all!) and feeds her table scraps instead of dog food. Oh yeah and she is crawling with fleas) She is a sweet dog though. A Jack Russell may suit you to, even if they chase the chickens at first they are really smart and can more than likely be trained to leave the chickens alone pretty quick. What sort of a dog do you want? Small or big? Long hair or short? Colors? House dog or outside dog only?
P.S. Yes I'd say herding dogs would be best. They are generally very smart and eager to learn, and if they are fed well they are not in for the kill, just a little herding fun. German Shepherds, Collies, Border Collies, Shelties, Australian Shepherds...
