Theme 17-12 is a level with a Golden Egg. Hit the tresaure chest for a golden egg. Use a Yellow bird to get it.
Fire the Red bird into the vertical pile of stone towards the right side of the level. This will cause wood to topple onto the TNT, clearing the right side. It is a tough trajectory to go below the stalactite and above the roof of the second structure, but it is possible. With a similar trajectory, bomb the right side of the left structure and ricochet the White bird into the stalactites above the second structure. If necessary, use a Yellow bird to clean up.