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Tiny tunes: Birds sing short songs due to traffic noise

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etc 5th lead- april 19

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.
Although making adjustments helps get songs across when traffic noise increases, birds hearing the altered calls might not respond as strongly to them, thus reducing the abilities of males that adjust their songs to attract a mate and defend a territory.
By offering relief from traffic noise, temporary road closures provide birds with the opportunity to sing the version of their song that optimizes vocal performance, mate attraction and territorial defence. While a uniform reduction in traffic noise is ideal, road closures are helpful and could form part of an effective conservation strategy, the authors say.