Birdday Party (Birthday Party) level 18-2 is quite challenging. The best strategy is to use the Orange bird to hit the very-bottom-left of the wooden triangle of the top-right structure. If you only clip that wood, the structure should topple left while dropping the Orange bird to the middle structure before expanding. If successful, at most two pigs should remain: dead-center and top-right. Use a high-arcing shot with the Yellow bird to reach the top-right pig. Finally, use the bomb from the White bird as close to the middle pig to clear the level. The score in the video below is 85,660.