I had the good fortune to acquire a 3/4 border collie 1/4 English shepherd pup from a ranch in Wyoming April 1991. The pups were born outside in February and had never been inside. I was doing telemetry research and was in the field every day, and it was a bumper grouse year in the Bighorn mountains. Once the broods could fly I started putting her on them every chance I got, and in September 1991 we shot over 100 grouse over that 7 month old dog. Her hunting drive was ferocious her entire life, and she was a joy to hunt with. She would hunt a cripple relentlessly, rarely lost a bird no matter how poorly hit. She retrieved ducks fearlessly and would dive for cripples.
I've had four good "bird dog" breeds, two of which were good hunters, but never a dog with her drive and desire. I'm in total agreement with Bluemoon on the benefits of getting a pup on lots of birds young to create a driven hunter.