My rescued (shelter) dog chases squirrels, birds, rabbit, deer, chipmunks, woodchucks, and even a local skunk (at least three times this summer). She also got excited and ran around their pen in the shed once the chicks grew out of the brooder.
For these reason, I was wary of letting our chocolate lab around the chickens once they were old enough to free range. I let the chickens out - ready to call Cee Cee down. As the chickens darted away and around the garden shed, Cee Cee took off running. She stopped in front of the chickens as if to head them back where they belonged. I called her a good girl and let her know the birds were to be free in the yard. That was the only time she ran with the chickens.
She will let the hens walk right over her if she's laying down. But if she hears a distress noise, the dog will race to see what's wrong.
Yup! My chocolate lab would protect the chickens from dangers in the yard.
Love, Linn B (aka Smart Red) Gardening zone 5a - 4b in south-est, central-est Wisconsin