"Yes" Sirius said proudly. "The thunderbird is in his soul. It was meant to be. Bolt-shaped scar and all that rot..."
All the watchers waited impatiently to see Harry Potter's first change.
Black trained him for two years. With unusal calm for his wriggling self. He explained him the theory, all the possible forms and mistakes.
After a few months it turned out that, when angered, Harry produced small bolts of lightning between his fingertips. It was then, that Sirius reached to the conclusion that because of Harry's love for flying his animagus form had to be a thunderbird.
Now, he stood with his godson on the center of the field, waiting for him to transform. The sky opened and a lightning ripped out. Harry started to change.
The audience held their breath.
A yellow, mouse-like creature looked at them innocently.