Golden Egg #11 is located in Level 1-6: Zoom out. The Golden Egg is on top of the hill on the far right side of the screen. Fling a yellow bird at just the right angle then hit a speed burst to hit the Golden Egg (→ see image).
Note, this is a two part video. The first part shows how to find the Golden Egg and the second is a walkthrough on how to pass the actual Golden Egg level.