Your dog has to be interested before you can build up the desire. Your dog is still young and the interest is in playing games. Go someplace where you can buy a small bird like a quail. Tether it's feet to along cord. Let the dog have at it. Play with him, tease him. If he catches it, don't worry; you are just building up his desire for birds. The dog can do no wrong at this stage.
If the dog is disinterested then it either don't have the mentality to hunt or is still too young. BTW, make sure the bird is small. You want the dog's experience to be fun and not a battle.