I have three Australian cattle dogs, and honestly like any dog it's going to come down to training and the dogs temper/attitude... My eldest male is 180 degrees a different dog then his half sister, and our newest one is still a puppy, he seems to feed off of whatever the closest dog is doing at that moment...
Anyway I'm in pretty much the same boat you are in right now, need to not only introduce them to the chickens, peafowl and guineafowl but also my goats and llamas... Right now as of last month the goats/llamas are in an adjacent pasture to the dogs, the female Heeler will walk that fence and bark at them if they get say within say 50 feet, the male Heeler doesn't give a hoot or second look anymore and the puppy copies the nearest dog... I have no doubt that with limited 1:1 exposure and time they will coexist with the goats/llamas and even my flock of birds but it's not going to happen overnight... It's going to take some schooling on my part, but Heeler's do have a strong 'protect the herd' instinct and once you get them to realize the birds are part of the family they should be fine and even babysit them... I also have to school the llamas as they have little love for any K9, but so far seem to be tolerating and/or even ignoring my dogs, funny as they absolutely hate my brothers dog and have from day one, they will charge that dog and get ready to unload the spit every time they see it...
Also my old neighbor had 3 hens (I lived in a neighborhood so they were only a few feet away) my dogs didn't' seems to give them a second look after a few weeks...
The one thing I know all too well about my Heeler's is that their herding skills and herding desires are hard wired in their brains, mine have never been working dogs but they know full well how to herd and want to do it, even to me and my daughters... You might find this the hardest thing to break even if they do get along with your birds, as you might find them running the birds to death or as you said having a 'job' as they herd the chickens around all day... This can be broken but it takes some work and at least for me my dogs they will regress back to herding instincts if you don't keep up on it, they herd my daughters around constantly if I'm not watching them as the daughters don't discipline the herding behavior...
BTW congrats on the dog, I have found the best 'toy' for Heelers (since they need a job) is a 10" Jolly Ball (aka horse ball) I'm talking about the no handle one just a hard round plastic ball... My dogs will chase/herd these balls all over the pasture as if they were trying out for the world cup, and they are indestructible... Seems like every other toy I have given them becomes a "How fast can I destroy this?" job to them...