Research has uncovered that traffic noise pollution has detrimental impacts on baby birds, affecting them even before they hatch.

The study revealed that exposure to the sounds of city traffic, such as revving engines and passing cars, can lead to long-term negative effects on the health, growth, and reproductive success of birds.

“Sound has a much stronger and more direct impact on bird development than we knew before,” said Dr Mylene Mariette, a bird communication expert at Deakin University in Australia and a co-author of the study, published in the journal Science. “It would be wise to work more to reduce noise pollution.”

The research team, led by Mariette, investigated how zebra finch eggs and hatchlings responded to different auditory environments. They exposed the eggs and newborn chicks to three different conditions: complete silence, soothing zebra finch songs, and city traffic noises. The exposure for eggs lasted five days, while chicks experienced the noise for about four hours nightly for up to 13 nights. Notably, the parents of these birds were not subjected to the noise.

The findings were significant. Eggs exposed to traffic noise had a nearly 20% lower likelihood of hatching. Chicks that hatched under these conditions were more than 10% smaller and nearly 15% lighter than those not exposed to traffic noise.

Further, analyses of the chicks’ red blood cells and telomeres—a type of DNA that shortens due to stress and aging—indicated more significant erosion and shorter lengths compared to their counterparts.

The impact of the noise exposure persisted beyond the initial exposure period and affected the birds into their reproductive years. Birds that had experienced noise disturbances early in life produced fewer than half as many offspring as those that had not been exposed to such stress.

“We were expecting some effects, but we didn’t expect them to be so strong,” said Mariette, especially because the exposure to noise pollution was relatively mild and for only four hours a day. “It was really quite striking.”

“We generally assume, based on numerous studies, that very young birds, especially in the egg, have very poor or no sensitivity to sound,” said Robert Dooling, an animal hearing expert from the University of Maryland in the US, who was not involved in the study. But “this study raises the spectre of broad, negative, enduring effects of noise on development”.

This study contrasts with findings by Hans Slabbekoorn, a professor of acoustic ecology and behaviour at Leiden University, who did not find similar growth impacts in chicks when both the chicks and their parents were exposed to moderate noise pollution. Slabbekoorn suggested that changes in parental behaviour, such as increased attentiveness to the nest, might mitigate the negative impacts of noise.

“I was indeed not expecting [such a] big impact necessarily,” Slabbekoorn said. It is the cumulative nature of these negative effects that may “in the end be most problematic”, he added. “Especially when noisy conditions are indeed frequent or continuous, as with birds living in noisy neighbourhoods, close to airports, or busy highways.”

His observations also highlighted that birds living near airports could be experiencing partial deafness due to the extreme noise levels.

Despite these insights, further research is necessary to clarify the specific aspects of traffic noise that are most disruptive—be it loudness, pattern, pitch, or other factors—and to determine how broadly these findings apply across different bird species. This growing body of evidence points to the profound and pervasive effects of noise pollution on wildlife, emphasising the need for comprehensive studies to understand and mitigate these impacts better.

 

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