Some dogs have a propensity for a little hard mouth. He may have been whacked by a wing or had a bird peck him. I think the more he retrieves the less the problem will occur. Don't use a shock collar for this problem, you might end up with a dog who won't pick up a bird. I used to use a collar on my GSP's but I found that they do more harm than good. I finally sold mine. Better off with a whistle.
I trained with whistle and collar. The problem I encountered was when I hunted with other hunters and they used whistles or on publics areas and hunters in the general vicinity used whistles. Too confusing for the dog and I tried to find a whistle with a unique sound. I noticed pressured birds, especially pheasants and chukars, seemed to use dog whistle as a warning system and exit the area when they hear it. I like to hunt as quiet as possible and even limit voice commands.
I use a collar with beep function for mostly dog safety reasons
I just let the dog hunt and maybe make a few corrections a day or when I need her to heel when trying to enter an area walk a distance and not spook pressured birds.
I train my train and expect my dogs to hunt with me and not hunt for themselves. I expect the dog to know here I am and look back and hunt together.
A pet peeve of mine is hunting with professionally dogs who take off after released from truck and run ahead and keep busting birds. A lot of times I am watching guys' dogs busting birds a 100 or 200 yds ahead and they are not even paying attention to their dogs. Arrrhhhg!
