You will need to be very careful. All dogs, even tiny ones, have prey drive and chickens will trigger that. You shouldn't let them alone with chickens. I have Shih Tzu and even though the chicks grew up with the dogs , I know the dogs could be triggered into attacking them if I am not there. Everything is fine when I am there and the birds and the dogs will nap lying together on warm sunny days . Often the hens will put their heads over on the dogs back, but I never let them alone with them. The chickens have a big fenced area just for them and the dogs go into their space only when someone is with them. Maybe a herding type of dog that can be trained to protect livestock might be ok, but still I would keep an eye on them. My Grandmother had a farm dog when I was a kid that herded all the animals and would even round up the chickens and ducks and get them in if she thought it was time or if she thought there was danger. Dogs are by nature predators and chickens are a prey animal so you always have to be careful having both.