City life drives birds to change their tunes, recent research shows.
A new study says that birds living in major cities sing shorter, faster songs that are higher-pitched than those sung by their brethren in the forests.
The researchers think that the birds adjust their songs to allow themselves to be heard over the din of the city, especially the low rumble of traffic noise.
To study how urban birds sing, Hans Slabbekoorn and Ardie den Boer-Visser, biologists at the University of Leiden in the Netherlands, traveled around Europe and recorded bird songs in ten major cities and in nearby forests.
The species they focused on, the great tit, is widespread across Eurasia and one of the few types of birds that thrives in big cities.
Singing is crucial for males, which use their songs to attract mates and mark out their territory.
The changing songs could play a role in eventually causing the city birds and the forest dwellers to evolve into separate species, Slabbekoorn speculated.
The findings could also help explain why usually only a few bird species thrive in cities. By contrast, many more bird species tend to be found in forests and other undeveloped habitats.
From London to Prague
From London to Paris, Brussels to Prague, the songs of the great tits living in cities all showed the same kinds of changes.
"I was surprised it was so consistent," Slabbekoorn said.
"The only explanation is that there must be quite a strong selection pressure," he added, meaning that the birds gain a big advantage by changing their songs to suit their environment.
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