Just aim towards the middle floating island based on our picture. This is an easy stage that should not take you too many tries to achieve three star mastery.
Power Activation Point
Activate your boomerang while in mid air. The boomerang hit should kill all the birds on the upper right cliff.
First Shot Result
Some of the metal pieces fall on floating platform. The platform brings down the left tower. The bomb gets triggers and all the birds die as a result. The three star mastery is then yours to keep.