Birds sing shorter songs in response to traffic noise
Birds sing differently in response to traffic noise, which potentially affects their ability to attract mates and defend their territory, according to research published in Bioacoustics. The study found that a species of North American flycatcher sings shorter songs at a lower range of frequencies in response to traffic noise levels. The researchers suggest traffic noise reduction, for example through road closures, is a viable option for mitigating this effect.
Dr. Katherine Gentry of George Mason University, Virginia, USA and colleagues studied the song of the Eastern wood pewee (Contopus virens) in three parks within the greater Washington, D.C. area. Songs were recorded at sites where the traffic pattern of the nearest road was either relatively constant or reduced on a weekly basis during a 36 hour road closure.
The bandwidth, duration, and maximum, peak and minimum frequencies of the birdsong was measured and analysed, together with low frequency traffic noise amplitude within 20 seconds of each song, and full-spectrum background noise levels.
The researchers found that the birds immediately responded to fluctuations in traffic noise by adjusting the length and frequencies of their song in order to improve its transmission. When roads were closed, songs returned to their natural state with broader bandwidth, lower minimum frequencies and longer duration.
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Image credit: Dr. Katherine Gentry