Yep, dogs are dogs, and dogs are predators. I have five dogs, three of whom probably wouldn't bother the chickens - unless something startled the birds and made them squawk and fly. The other two dogs would run them to death trying to herd them. Even a dog who's not trying to hurt the birds can kill one by accident. I know there are dogs who are fine with chickens, and even protect them, but I wouldn't trust my dogs around loose birds. My Newfoundlands are retriever dogs, too, like your lab, but they could injure or kill a hen, or especially a chick, just trying to bring it to you.
The dog who's licking it's lips when the chicks are near is showing stress and nervousness. The dog isn't sure what those fuzzies are, doesn't know what to do about them. I'd suggest you show her what you want before she tries to figure it out on her own. Take her out on a leash, with a handful of yummy treats, when she looks at a chick tell her firmly, "No, leave it", and when she turns her head away from the chicks, and looks at you instead, give her a treat and praise. Then walk her all around the chicks, getting her to pay attention to you instead of them, with treats and praise when she ignores them. Just for a few minutes at a time, several times a day, for several days. When she's really good at that, take her out near the chicks and just hang out, with the dog lying next to you. Same thing, praise her for not bothering the birds.
If you have a helper, the next step would be to have the other person hold a chick in their hands so the dog can't grab it, or hurt it in any way, have them walk up to the dog holding the chick, same routine with saying No leave it, treats and praise when she does. YOu should see the lip-licking stop as she learns that she doesn't need to do anything about those llttle fuzzy-butts.
I do agree with the others, you should make your coop more secure - you don't want your chicks running around loose and unsupervised no matter what. But having your dogs comfortable around them is important, too.
When we walk our dogs every day, we pass the chicken coop to get to the trails in back. I leash my Australian Shepherds until we are well past, as they run laps around the coop, I think trying to herd the birds. It makes the chickens nervous, the roosters run the girls inside and stand guard at the door to keep them safe. The dogs would be likely to hurt the chickens, but remember that beaks can cause a lot of damage, too. Loose chickens don't have to happen, if your coop is secure. Keep everyone safe!
Good luck.
