Some dogs have incredible prey drives and some don't. I have two dobermans, both were mildly interested in the chickens when they first met. One chicken was killed by my first dog, I disciplined him about 20sec after the fact- he would not look at the chickens for a week, and would not go near them for longer. They have low prey drive, and are now completely trustable with the adult chickens. The chicks are more interesting to them when they jump around, but so far I have not had to intervene. I have taken care of some terrier types- and they had very strong prey drives, and just about strangled themselves trying to get to the chickens. I would not keep a dog like that as long as I or my neighbors chose to have chickens, as it would be a recipe for disaster. I think in this case, if a really secure separate area cannot be created for the chickens- either the remaining chickens or the dog(s) need to find a new home. Too dangerous for the animals +/- the human relationship to have a shared chicken/dog area.