Urban birds raise their voices over the din July 17, 2003
Great tits (Parus major) in noisy cities generally sing higher notes than their counterparts in quieter locations. Urban birds could use the ploy to ensure that their mating calls are heard above the racket. Writing in a Brief Communication in the July 17, 2003 Nature, Hans Slabbekoorn and Margriet Peet report that great tits in Leiden, The Netherlands, sing songs with higher minimum frequencies if their territory is noisy. Birds in quieter spots, on the other hand, more often dip to the bottom of their vocal register. Great tits commonly adjust their songs once they have claimed a breeding territory, the authors point out. City-dwelling birds may therefore be tailoring their songs to ensure maximum success against the background of low-frequency urban rumblings. The researchers add that species lacking the ability to adapt in this way may find it difficult to breed in built-up areas, and could decline as a result.
Hans Slabbekoorn, Leiden University, The Netherlands
Song from quiet territory
Song from noisy territory
The sonograms above show time on the x-axis and frequency (pitch) on the y-axis. The color scale shows the amplitude of the sound: red is loud and sound becomes fainter from yellow to blue to black. The sonogram at left is from a great tit that lives in a quiet terrotory. The sonogram at right is from a great tit that lives in a noisy territory. To hear the song of each bird click the player below each sonogram. In the recording from the noisy territory one can hear the noise of traffic; this traffic noise is visible in the sonogram as bands of color in the lower part of the sonogram.
Note that the song of the bird from the quiet territory includes lower pitches than the song of the bird from the noisy territory. (Lowest pitch in sonogram at left is about 3kHz; lowest pitch in songram at right is about 4kHZ).
