You may also want to think about starting them out with a smaller bird like chukars and quail. Pigeons are cheaper, fly back home, and have more scent but depending upon the puppy size, smaller birds won't startle your dog as much whenhe is flushing it.

Personally, I wouldn't worry too much if he doesn't show any signs of birdiness at a young age. My setter didn't either.She started at 4 mo. or so, more like 5 mo. From showing no interest in birds to being totally head strong about them in about two weeks. But when that switch comes on, the more birds you feed him the more birdiness it's going to show.