From a light twitter to a mechanical roar
Report finds urban birds are mimicking traffic noises
For several months now, even before the sun rises, a male blackbird has been shattering the pre-dawn silence of the quiet Somerset region of southern England. This bird's morning song is no normal twitter, but rather perfect imitations of the most irritating noises - car alarms, ambulance sirens and even cellular telephone ringtones.
An article published this week in the Conservation, the magazine of the American Society for Conservation Biology, reveals that this blackbird is not unique, but rather part of a growing phenomenon among songbirds (in addition to crows, whose mimicry prowess is well known to science). Feathered friends are adapting to environments full of foreign noises by mimicking them and adding them to their repertoire of melodies.
One prominent researcher of this new musical style is Dutch scientist Hans Slabbekoorn. At first he was skeptical of the reports of the birds imitating traffic sounds, and asked people to send him recordings. He received recordings of birds mimicking the traffic around them, including the distinctive sound of a golf cart backing up - produced by blackbirds living near a golf course.
The reason for the blackbirds' amazing vocal ability is a gift from Mother Nature - it helps them attract females. That ability also apparently works for the human species.
"There is a blackbird in Jerusalem's Sacher Park that imitates the whistle sounds men make at girls, and has simply incorporated those sounds into his regular songs," says Amir Balaban, of the Society for the Protection of Nature in Israel, noting that girls even turn their heads at the blackbirds' whistle.
Bird researcher Dr. Yossi Leshem of Tel Aviv University, says the Israeli champion at imitating urban noises is the Eurasian jay.
"This bird used to live in forested areas, but gradually spread to the cities," says Leshem. "It is an amazing mimicker and specializes in car noises."
In some cases, the environmental noise is a real obstacle for the birds, and they are forced to change their singing habits. In recent years, the robins in Sheffield, England switched to singing at night, because they could not hear themselves during the day.
"If you hear a bird singing on your way home from a night at the pub," says University of Sheffield scientist Richard Fuller, "it's probably a robin."
In Berlin, the nightingales have begun singing louder, in response to the traffic noise. Other birds have begun singing at higher frequencies, to be heard over the lower frequencies of man-made sounds. Slabbekoorn says that some birds, such as the golden oriole, have been unable to adapt to the acoustic challenges of their urban environment. Slabbekoorn fears that this inability to change the pitch of their song will threaten their survival. The article in Conservation also notes that some birds in the West African jungle have begun singing at lower frequencies, in order to be heard over all the high-pitched insect sounds.
In Jerusalem, Balaban says urban noise has forced the partridge to alter its courting habits. In one of the capital's valleys partridges have stopped singing to attract females, because of the intrusive noise of the buses. Instead, the male partridges have begun to sit on tree branches where they can be seen better.
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