Included in the Timber Tumble update to Angry Birds Rio (v2.2.0), there’s a super secret episode hidden! This episode is called Hidden Harbor and includes an extra 15 levels!
If you haven’t found it on your own, hopefully our walkthrough will help. Head over to Timber Tumble Level #14. Notice the angled slopes to the left of the slingshot platform? Toss the Yellow bird down the slopes. There’s a Golden Lock hidden in the bushes at the bottom, which unlocks Hidden Harbor!