Angry (City) Birds
A new study shows that urban Song Sparrows are much more aggressive than their rural counterparts.
鈥淵a talkin鈥 to me?鈥 City dwellers are known for their in-your-face attitudes鈥攕omething that holds equally true for humans and birds, researchers report.
During a multi-year study, published recently in the journal , researchers from Virginia Tech played taped song recordings of unfamiliar male Song Sparrows to breeding male Song Sparrows in contrasting environments in southwestern Virginia. Their finding: Birds in crowded towns respond much more aggressively to the 鈥渋ntrusion鈥 than those in parks and on farms. The urban birds spent more time zooming at, and perching right next to the audio speakers than their country counterparts. (Hello, road ragers, sound familiar?)
鈥淚t fits in with what we see in humans these days,鈥 says study co-author Ignacio T. Moore, a professor of biological sciences at Virginia Tech. But motivation for aggression is the key difference between humans and birds. Raised tempers in cities can stem from the crowds, along with 鈥渢oo much work and not enough free time,鈥 says Moore. In Song Sparrows, food appears to be the driving factor.
Moore and his colleagues figured this out by supplementing Song Sparrows鈥 diets with birdseed. They discovered that when the rural birds had additional food to fight over, they started acting more like the urban birds.
The researchers have two theories to explain the finding: Access to abundant food saves time and energy that would be spent foraging, making room to invest more in territorial defense. Alternatively, higher pressure from competitors rushing in for food could be making the residents hostile. 鈥淢aybe, if you have a better territory, you have to up your game to defend it,鈥 Moore says.
The researchers also looked at Song Sparrow population density and at the abundance of prime nesting materials, but neither of those factors appeared to play a role in heightened aggression.
As urban development expands worldwide, studies considering how wildlife responds to changing landscapes will become increasingly important. 鈥淭here are big ecological and behavioral and conservation questions to be answered,鈥 Moore says. Adapting to city life is a challenge; if the sparrows are getting a little hot-tempered because of it, who can blame them?