It is possible to clear Danger Above level 6-4 with a single bird. The strategy is to fire the Yellow bird low, through the wooden legs on the left side. The structure should begin to topple as the Yellow bird rolls back to the left. Then sit back and hope that all three TNT detonate. The score in the video below is 84,500.
Fun fact: This level reveals the Boomerang bird, trapped in the middle of the level. Our video does not show him because this level was recorded in hindsight. Check out Rovio’s official walkthroughs on YouTube to see him.