Mine have learned to recognize the dogs that should be here, even though they don't care for the pups much yet. But we had a visitor dog come up the other day -- and was far, far too interested in the chickens for my taste -- and the chickens all screamed bloody murder. Luckily I was outside and grabbed the dog before it could do anything, and my dogs distracted it enough to let me get in there. My chickens also don't react to the next door neighbor dogs, who roam over here, to my frustration, but those dogs don't bother the birds one bit.
RR and Sunny - that's good to hear on the "foreign dogs". I have just read other folks say they thought having their dogs around desensitized their chickens to dogs. They said that their chickens became "dependent" on the dogs and then if another one came around they viewed it as "friend" rather than foe.
I'm glad to hear that you haven't had that experience! And it's good to get the other side of the story.