Bwahaha... Reflect the confuse ray right back at him (ray = beam.. beam = get reflected). Giga Drain and Drill Peck need physical contact (read ASB Attack List) to work. To prevent that, shoot a barrage of ice at the weak bird. Use two blizzards. It'll slow the birdies movement, push it backwards, numb it, AND Natu will either have to not use either attack, or get hit by the full force of the Blizzards. BWAHAHA!
Reflect~Blizzard~Blizzard