rob,
Thats awesome your dog is into the birds. Keep him birdy, make it fun for him. Shoot a duck and freeze the whole thing and get him used to fetching that. When you are done with the bird, put it back in the freezer.
Some will say it is wasting a bird, in my experience sacrificing one duck for training will save MANY cripples throughout the year. I like listening to guys tell me how bad it is to waste a duck on training, then watch them lose a few cripples each day.
Mike