Abstract
The ubiquitous anthropogenic low‐frequency noise impedes communication by masking animal signals. To overcome this communication barrier, animals may increase the frequency, amplitude and delivery rate of their acoustic signals, making them more easily heard. However, a direct impact of intermittent, high‐level aircraft noise on birds’ behaviour living close to a runway has not been studied in detail.We recorded common chiffchaffs Phylloscopus collybita songs near two airports and nearby control areas, and we measured sound levels in their territories at Manchester Airport. The song recordings were made in between aircraft movements, when ambient sound levels were similar between airport and control populations. We also conducted playback experiments at the airport and a control population to test the salience of airport, and control population specific songs.In contrast to the general pattern of increased song frequency in noisy areas, we show that common chiffchaffs at airports show a negative relationship between noise exposure level and song frequency.Experimental data show that chiffchaffs living near airports also respond more aggressively to song playback.Since the decrease in song frequency results in increased overlap with aircraft noise, these findings cannot be explained as an adaptation to improve communication. The increased levels of aggression suggest that chiffchaffs, like humans, might be affected behaviourally by extreme noise pollution. These findings should influence environmental impact assessments for airport expansions globally.
Highlights
Animals, like humans, are negatively affected by the global increase in anthropogenic noise levels (Barber, Crooks & Fristrup 2010; Shannon et al 2016)
Sound levels generated by aircraft movements measured at chiffchaff territories at Manchester airport varied between LAFmax 67 and 118 dB(A)
Chiffchaffs holding territories near Manchester airport runway 2 are exposed to extreme sound levels, frequently exceeding LAFmax of 110dB(A)
Summary
Like humans, are negatively affected by the global increase in anthropogenic noise levels (Barber, Crooks & Fristrup 2010; Shannon et al 2016). Anthropogenic noise at the current level and scale is a pervasive (Buxton et al 2017) and relatively novel selection pressure that is projected to increase with human population expansion (Barber, Crooks & Fristrup 2010). Motorways produce diel patterns of peaks and troughs in sound level and reach maximum levels of approximately 65dB(A) along the linear structure of the road with the spectral energy concentrated below 2kHz (Halfwerk et al 2011b). Industries, such as resource extraction and construction usually provide a point source of noise and affect restricted areas.
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