Angry Birds Wave Their Wings Before a Fight

Most birds have their own territories that they defend throughout their year. They are territorial to their own species who share a similar code of conduct. A commendable trait in birds is that they do not make an attempt to trespass another bird's territory. And they seldom resort to physical combat, but if they do so, the angry birds can fight to death.

But a latest study reveals that the angry male sparrows initially wave their wings wildly in order to avoid a dangerous scuffle.

"For birds, wing waves are like flipping the bird or saying 'put up your dukes. I'm ready to fight,'" Duke biologist Rindy Anderson said in a press statement.

He continued saying that the male swamp sparrows initially used wing waves as an aggressive signal to defend their territories and their mates from other intruding males. These findings help in understanding how birds communicate with other males by combining visual displays and songs.

To understand this better, Anderson along with co-author, former Duke engineering undergraduate student David Piech, created robotic equipment that was stuffed inside a deceased bird. They created a robosparrow similar to the male swamp sparrow that could easily flip its wings like the live male sparrow.

The robosparrow was taken to a swamp sparrow breeding group in Pennsylvania and was placed in a territory of live males. The robosparrow sang songs with the help of a speaker that was fixed beneath the dummy bird's perch. This was a signal to alert the birds that he was intruding. The responses of the birds present in the territory were recorded by the team. Apart from this, the stuffed sparrow stayed stationary in one test and in the other it twisted from side to side.

From the tests it was clear that wing waves that are combined with songs are more powerful than a song of their own. Wing waves evoke aggression from live birds. An aggressive response was received from the live birds to the invading wing-waving robosparrow. If a bird wing-waved five times to the stationary stuffed bird, he would also wing-wave five times to the wing-waving robot. 

They found a consistency in the level of aggressiveness the males display.

The study was published online Jan. 28 in the journal Behavioral Ecology and Sociobiology. 

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