We got a red heeler last summer who keeps watch on our chickens whenever she is out, chasing off everything and anyone who enters her space. She has treed raccoons, weasels, fisher cats and who knows what else while we weren't watching. In 2014 we lost birds to raccoons, coyotes, and a particularly persistent mink but the only lost bird this summer was while we were out of town and our dog was with us. She was very interested in the birds when we first got her but we were able to train her to leave them with a little diligence. She does occasionally try to play with the birds but it is obviously not aggressive, just playful. Our rooster tries to attack her occasionally but she thinks he is playing and seems to enjoy it. Again, she bats at him like a cat and chases him playfully but ultimately he leaves her alone and she moves on.
Heelers are smart dogs.
Glad that it works for you, heelers are great dogs, but just as the name says, they are by no means livestock guardian dogs. Lgds are not interested in the animals they guard, though they occasional smell at their butt, as they do with the cats. Though quite sometimes the lay more or less next to or inside the chicken crowd, if there is something they are curious about they get up and hurry through the chicks, who try to free the path asap, as if they wouldn't exist. The chicken are never annoyed with the dogs, it seems they know they are protecting them. We are inside a huge forest and have all kinds of predators, including wolves, were some heeler might be to small as protection?
They do not play with the chicken, who mostly can even steal them food just as the cats, only if the dogs are pretty hungry (seldom), they shake their heads at the chickens.