Birds living in an urban jungle have adapted to the noise and pace of city life. They’ve altered their songs to be heard above traffic, become more bold and better problem solvers. But the price of some adaptations is less success at winning mates. Today’s nature news collection focuses on birds in cities. Next collection is from OceanDiver on April 13th.
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After at least a century, ravens are moving back to the nation’s capitol
Ravens are nesting in Washington D.C. for the first time in 100 years. They’ve been seen flying over DC a few times in the past, but presumably were chased off by hawks or bald eagles. This year, a nest was discovered under a bridge crossing the Potomac River.
Typically, ravens make their nests in mountains or cliffs. And ravens had pretty much disappeared from a number of mid-Atlantic areas for years. The closest they have been known to live to the D.C. area is parts of West Virginia and Sugarloaf Mountain near Frederick, Md. [...]
“They think they’re up on the side of a mountain face, nesting in a cavity,” Rauch said. “They don’t know it’s a bridge.” [Dan Rauch is a biologist with the District’s Department of Energy and Environment.]
I believe the ravens do know they are under a bridge and not on the side of a mountain. No fast food debris and traffic noise are found on a mountain side. No utility wires. Ravens are clever.
URBAN LIFE MAKES BULLFINCHES HEALTHIER, SMARTER AND NEOPHOBIC.
The town bird and the country bird: problem solving and immunocompetence vary with urbanization researchers examined the bullfinch Loxigilla barbadensis, a highly opportunistic and innovative endemic bird in Barbados.
They found that urban bullfinches were better at problem solving tasks like pulling open drawers to obtain food. Researchers said the they were better able to exploit new resources, which is how they survive city life.
Urban bullfinches were bolder, too, although they also were more neophobic (fear of new things), so it might take them awhile to decide a new resource is safe to exploit. Perhaps being bolder, they needed this caution to survive?
They also had a healthier immune system and the authors speculated this might be due to more exposure to novel pathogens.
City birds sacrifice song VIRTUOSITY for volume to be heard above traffic noise.
Audubon reported this study in Why City Sparrows Are Singing A Very Different Tune. And it’s not just sparrows altering behaviors in response to city life.
Other birds that live in and around cities have been found to wake up earlier, mate sooner, and generally be feistier than their rural brethren. [...]
Researchers from George Mason University analyzed the effects of urban life and “anthropogenic noise” (noise caused by humans) on male White-crowned Sparrows in San Francisco's Presidio park and found male sparrows are scaling up their tunes in order to be heard. . . .
Presidio birds have clearly shifted to a dialect more audible above the urban din. And they sing even that dialect at a higher minimum frequency than in past decades, likely in an effort to rise above the low-frequency rumble of cars.
So the guys are getting heard by potential mates but are they singing a mate-winning song?
Singing at a higher frequency may seem like a minor tradeoff, especially in a city with unlimited dining options. But it turns out the new song may not go over so well with the ladies. Male birds who upped their pitch had poorer vocal performance, and their song quality suffered as a result.
song quality more important than volume if you want to sound sexy
A study in the Netherlands found that by changing their tune, birds were less attractive to potential mates. (I added the bold because it’s a universal principle/sad reality that could motivate us to listen more closely.)
When bombarded by noise pollution, some male birds begin to sing higher tunes, found a new study. And that tonal shift makes them less attractive to females.
The findings suggest that birds must make difficult trade-offs in urban areas and places where traffic and industrial noises threaten to drown them out. Either they sing less appealing songs or tones in an effort to rise above the din, or they sing the songs that make them sound appealing at the risk of not being heard at all.
"If females can hear all song types equally well, they will go for the sexy ones, but if they cannot hear the sexy ones well anymore, then they might just go for the songs they can still hear," said Wouter Halfwerk, a behavioral ecologist at Leiden University in the Netherlands. "It could very well be that noise pollution is interfering with reproductive decisions by females.”
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