My cockatiel came to me with his wings clipped, and I always let him have them for a bit and to practice flying when they grow back and then go to get them to recut because he gets into a lot of trouble regarding flying... But I've noticed that when his flight feathers start to grow in that they usually grow in first on one side, and then after those are fully grown the other side starts. Right now his flight feathers on his right-wing have fully grown but haven't on the left... Does anyone know why this happens?