I feel for the frustration your going to go through, try it with 3 all puppies all part black lab. Two of those puppies learned rapidly that the birds are mine, the leader of that pack has been more pigheaded.
I caught him with one of my guineas the other day, holding it down, licking it. The lucky thing is that he soft mouths them instinctively so does no physical damage.
The thing that triggered forgetting his training was the adult flock of guineas going after the teenage flock. Since the adults are now part of his pack, the adults attacking the teenagers must be OK for him too.
His leader was hot. She would not talk to him or look at him but praised his brothers. He watches me like a hawk until I will finally acknowledge him, usually the next day. Then we go on for months without any problems.