USA Today on BuckbeakMovies
The USA Today has an article about the making of Buckbeak for the Prisoner of Azkaban film.
"We had a beak on a stick when we shot so that when Dan touched the beak, we got the right curvature of his hand," says Mark Radcliffe. "We had a horse there for the visual-effects people to get a sense of the light coming through the trees on that day. That light had to be replaced exactly when we were creating this three-dimensional creature."