It's kind of a visual trick. There are metal weights in the tips of both wings, and the rest of the body is hollow plastic. They balance that so that there's the same weight in front of the beak as there is behind it. If you look at it from the side, you'll notice that the beak is not at the front, it's significantly behind the wings. The wings and body are also curved slightly downward, so the center of gravity right below the beak, which is the most stable balancing situation you can have.