Birdday Party 18-6 (or Birdday Party Cake 2 Level 6) is the sixth level in Birdday Party. There is a Golden Egg trapped in a piece of wood at the top right in this level. See this page for more information about that Golden Egg.
Fire the Blue bird horizontally, splitting to do as much damage to the left tower as possible. The majority of the tower should topple to the left. Use the next Blue bird horizontally again, destroying some of the ice from the middle structure and clearing a path for the last Blue bird. With this bird, take out the bottom-left of the right tower. It should topple to the left and destroy all remaining pigs.