The dog more than likely never will point a wing hidden in the bushes...his nose is so keen that he completely knows the difference between the wing (dead meat) and a live bird (which can get away). I would not be discouraged by this behavior in the least.
That being said, you need to make sure he will point live game, and the only way to do that is to get him into birds. Wild birds preferably, but pen-raised will do if they are strong flyers.
You should also do " whoa" training. It is nice to know you can stop your dog on a dime no matter what the circumstances. See a recent previous thread for some basic instruction on this command.
If he is finding the wings, he obviously has at least a decent nose so there is still some hope. Get him into some wild birds real soon and see how he does. Make your decision about the dog based on this experience rather than on the wings in your back yard.