I agree with Pete on the correction issues.
If your young dog is chasing tweety birds let him, he will eventually bore of this and get interested only in gamebirds. I believe it is important for the dog to come to that on his own, NOT ELECTRONICALLY. You risk having the dog lose intensity or drive if you shock at the wrong times, particularly if the dog is "shy" at all.
If you want the dog to work closer, use your check cord and plant birds so he understands that being around you is where he can find birds. Every dog matures at their own rate, just like humans.
Go easy on the electronic correction.
Good Luck!