Parabeak

The Boomerang Bird (Sometimes referred to as Green Birds) are a species of birds used in Angry Birds, starting from Theme 6-5 (part of the episode Danger Above). These birds are shown to be in captivity, as a single Boomerang Bird is enslaved inside a cage in Theme 6-4 by four Pigs. With the help of some Big Brother Birds, the Boomerang Bird escapes captivity and calls on his relatives to join the Birds on their quest to rescue the Eggs. Later, in The Big Setup, the Boomerang Birds are re-captured alongside the other Birds, but they soon break out thanks to the efforts of a Big Brother Bird. Once again, the Boomerang Birds help their fellow Birds escape capture.

The Boomerang Birds' main ability is to swap directions in mid air. When the screen is tapped, the Boomerang Bird will open its large beak and proceed to head backwards and strike areas that the other Birds can't reach. Besides this, the Boomerang Birds are fired much differently than the other species. When they launch, they're constantly spinning, and they're launched at a farther distance.

Advantages and Disadvantages
The Boomerang Bird is very good against wood and glass, but not great against stone. When its ability is used, it's often the longer (eventually a set time) the bird can break through entire columns of wood and glass.

A common disadvantage is when the bird is fired straight into the air, it's hard to arc it perfectly when it approaches the ground.

Trivia

 * Boomerang Birds are stylized after toucans and hornbills.
 * A strategy to do incredible damage upon firing this bird is to fire backwards and quickly tap the screen.
 * They haven't yet appeared in Angry Birds Rio.
 * They'll also appear in the 2012 Angry Birds film.