Some clever chaps have recently discovered quite a few Angry Birds Seasons acheivements in the Game Center, that might be hinting at the angriest bird of all making an appearance on the iPhone – The Mighty Eagle!.
The achievements can be unlocked by buying the eagle in an in-app purchase, and by collecting 30, 60, and 120 feathers. (check out the screenshot)

Once you’ve purchased the Mighty Eagle, you can lure it into play by firing none other than a tin of sardines from your catapult. The destructive winged beast will then fly downwards, once every 60 minutes, destroying the levels scenery in its path…. and of course, any green pigs that happen to get in its way.
You are then awarded a feather should you manage to attain 100% destruction!
Keep your eyes open for the Mighty Eagle in Angry Birds, its coming soon to an iPhone near you.