Birds living in cities sing at a higher pitch to reduce the impact of echoes from surrounding buildings, a new study has claimed.
Higher-pitched songs travel further in built-up areas because their echoes fade more quickly, meaning the following notes are clearer and easier to pick out.
It had previously suggested that great tits and other common birds raised their pitch in urban areas to distinguish their song from the low-pitch drone of traffic and machinery, but now scientists believe it could be a combination of the two.
“Our cities are packed with reflective surfaces, open spaces and narrow channels, which you just don’t get in woodland,” the Telegraph quoted Emily Mockford, a researcher from Aberystwyth University, as saying.
“Because sounds bounce and travel in different ways, birds have to use songs that can cope with this,” she noted.
The study also found that urban birds’ songs were heard more clearly in woodland than those of forest-dwelling birds, possibly because rural birds use clues like how muffled songs are to determine their distance from one another.
Another researcher named Dr Rupert Marshall added: “In woodland where trees and leaves obscure the view, many species of songbird can tell how far away a rival is by how degraded its song is.”
“In cities there are fewer visual obstacles and song doesn’t degrade as quickly, so city birds may just concentrate on being heard,” he noted.
The findings were published in the PLoS One journal.