Sometimes you just have to try the individual dog with chickens because it can be hard to predict. In July I adopted a Lab/Border Collie mix from a local rescue, who allowed me a trial period to make sure she was going to work out. Since a lab is a bird dog, I didn't know which way it would go, so I arranged for the rescue to bring her to our house and we went directly to the backyard to see how she would react to the birds free-ranging there. Now keep in mind that the chickens, upon the appearance of a dog they'd never seen before, started squawking and running in all different directions and kicking up a fuss. The then 8-mo-old Lab X kind of looked at them with a quizzical look on her face, like "huh - wonder what that's all about", and then turned her back to go and check on an interesting smell. Fast forward 6 months and she has never shown any more interest in them than that first day. They of course have calmed way down now, and wander around her quite trustingly. (The dog is completely OCD when it comes to balls, and when we throw the ball for her in the backyard we have to be careful where we throw it because she's likely to bowl a chicken over in her attempts to catch a ball in the air if we're not careful, but that is the only way I can imagine her possibly harming one.)