I have experience with birds that have been attacked by dogs. After the vet okays his basic health, you have to give him time to get over the shock. It is a terrible experience to be savaged by a predator, and some of his systems have shut down. He will get over it, as long as he isn't too physically damaged. I rescued a cockatoo that lost a leg and half her wing to a dog. She was okay, but, never very trusting or very friendly after that. There was probably emotional damage. She eventually trusted me enough to handle her, but, was a nervous bird. Please be patient, and proceed at his pace. Give him a good amount of quiet time, if he seems to want it. Also, if the dog is yours, keep him away from your bird. Do not traumatize him any more than need be. If I think of anything more, I'll let you know.