January 29, 2013
Scientists Create ‘Frankensparrow’ To Understand Bird Brawls
Lee Rannals for redOrbit.com — Your Universe Online
A new study has found male sparrows actually perform a little trash talk before engaging in a brawl to the death.Researchers wrote in the journal Behavioral Ecology and Sociobiology male swamp sparrows use wing waves as an aggressive signal to defend their territories and warn away intruding males.
Scientists previously thought the sparrows' wing-waving behavior was a signal intended for other males. However, this observation proved difficult to test.
The team built a miniature computer and some robotics, and then stuffed the devices into the body of a deceased bird, essentially creating a ℠Frankensparrow´ that looked just like a male swamp sparrow and could flap its wings as if it was alive.
Anderson took the Frankensparrow to a swamp sparrow breeding ground in Pennsylvania and placed it in the territories of live males. Their robotic bird "sang" swamp sparrow songs using a nearby sound system to let the birds know he was intruding, while the team watched the live birds' responses.
She also performed the tests with a stuffed sparrow that stayed stationary and one that twisted from side to side. These tests showed wing waves combined with song are more potent than just a song, and wing waves alone evoked aggression from live birds.
The live birds responded most aggressively to the invading Frankensparrow, which Anderson said she expected.
"What I didn't expect to see was that the birds would give strikingly similar aggressive wing-wave signals to the three types of invaders," she said.
If a bird wing-waved five times to the stationary stuffed bird, he would also wing-wave five times to the wing-waving robot.
Anderson believes the defending birds would match the signals of the intruding robots, but her team's results suggested the males are more individualistic and consistent in the level of aggressiveness than they want to signal.
"That response makes sense, in retrospect, since attacks can be devastating," Anderson explained.
Real males may only want to signal a certain level of aggression to see if they could scare off an intruder without the conflict coming to a fight and possible death.
The risk of severe injury or death didn't keep the males from swooping in and clawing at the robotic sparrow, whether it wing-waved or not.
"It's high stakes for these little birds. They only live a couple of years, and most only breed once a year, so owning a territory and having a female is high currency," Anderson said in the statement.
The team now plans to test how the sparrows use wing waves combined with a characteristic twitter, called soft-song, to show aggression and fend off competition. This experiment could be on hold, however, because Frankensparrow's motor is burned out and its head was ripped off in an attack.