Blue heelers (a.k.a. Australian cattle dogs) are a herding breed, not a livestock guard dog (LGD). As such they are bred to move and control stock, not guard it. Some herding dogs will guard livestock, but heelers generally have too much drive and tend to harass or chase stock when bored. This is especially a problem with poultry because it is so easy for a dog to injure a bird. It is always good to start with puppies, but even they need supervision for a long time--a flapping duck is just too tempting to chase.
Now if your ducks and geese are in a night pen and the dogs are outside the pen, the dogs most likely would chase away any predator that came close, or at least make an awful lot of noise.
True LGD breeds, like Great Pyrenees or Anatolian shepherds, should be raised from a very young age with the animals they are supposed to protect. This means living in with the stock 24/7. This is how they bond with the stock and come to regard them as pack members never to be hurt, and always protected. Well trained ADULT herding breed dogs sometimes can be trusted with poultry unsupervised, but their primary bond is with their humans and other dogs, not the livestock. They will be unhappy if confined with the livestock all the time.
