To survive the urban jungle, birds change their tune, with faster-paced and higher-pitched songs to make them heard above the din.
This discovery, announced Monday, could help reveal which birds can adapt to life in the city and which can't, researchers said.
Behavioral biologist Hans Slabbekoorn of Leiden University in the Netherlands originally investigated what effects noise in the rainforests of Cameroon had on birdsong. He reasoned noise in the urban jungle might similarly impact birdsong.
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Songs are often critical to male birds when it comes to attracting mates and warding off rivals. If urban noise drowns out bird songs, they might disappear from cities, Slabbekoorn explained.
A separate study last month found that noise affects the sex lives of birds.
Slabbekoorn investigated a relative of the chickadee known as the great tit, one of the most common birds in Europe.
Its songs resemble the sound of "a bicycle handpump when you inflate your tire," Slabbekoorn said.
Slabbekoorn traveled around Europe on car and on bicycle, recording great tits at 10 forest sites and the centers of 10 large cities nearby — everywhere from under the Eiffel Tower to next to Buckingham Palace.
"I stayed at camps, cheap hotels, but especially relied on friends where I could spend the night," Slabbekoorn recalled. "I would typically be outside between 4 a.m. and 5 a.m. to start recordings."
Slabbekoorn and his colleague Ardie den Boer-Visser found songs in all 10 cities were shorter and faster-paced than forest counterparts.
Urban birds also had higher-pitched songs, likely to get heard above the low frequency sounds of the roar of traffic.
While great tits can adjust their songs, that "may be their luck," Slabbekoorn said. Other species will "have to move out," he told LiveScience.
Slabbekoorn and den Boer-Visser reported their findings in the Dec. 5 issue of the journal Current Biology.
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