Dan Mennill, University of Windsor
April 20, 2026
When Rachel Carson wrote the environmental classic Silent Spring in 1962, she warned that unchecked human impacts might create a silent future.
Forty years later, biologists uncovered a striking effect of noise pollution on songbirds. They found that low-pitched traffic noise in European cities forced birds to sing at higher pitches. Songbirds in a noisy park beneath the Eiffel Tower sang at a pitch of 400 Hz higher than those in quiet forests outside Paris.
My new research, published in the scientific journal Ornithological Applications with colleague Hans Slabbekoorn from the University of Leiden, shows that Paris is a success story in the battle to reduce noise pollution.
Yet even as Paris has grown quieter, birds have not returned to their natural song frequencies. Our research shows that great tits in Paris continue to sing at higher pitches than birds in wilderness areas outside the city.
Further noise-reduction efforts are vital, in urban areas throughout the world, to allow wild birds to communicate at their natural sound frequencies.
The devastating impact of noise
Human activity fills the world with noise. The sounds of cars, airplanes, boats and industrial activities produce a steady roar that impacts wild animals, birds and insects. We often overlook noise pollution as a conservation problem, yet it may have devastating effects on wildlife during an era of increasing urbanization.
Road noise interferes with the ability of birds and frogs to attract mates. Boat noise leads to decreased vocal communication in whales. And traffic noise influences predator-prey interactions between moths and bats.
Since the discovery that low-pitched traffic noise in European cities forced birds to sing at higher pitches, this pattern has been demonstrated in diverse bird populations around the world.
Savannah sparrows sing higher-pitched songs near noisy oil pumps on the Canadian Prairies. European robins sing higher-pitched songs in the presence of wind turbine noise. And Australian silvereyes sing higher-pitched songs and calls in loud urban areas compared with rural areas.
These changes diminish birds’ ability to defend breeding territories and attract mates.
Fighting for a quieter city
Paris is one of the largest and most densely populated cities in Europe, yet Parisians have developed novel strategies to fight noise pollution.
The city has converted many roadways into bicycle lanes and installed anti-noise coatings on major roadways.
Automated noise cameras issue fines to excessively loud vehicles. A regional observatory called Bruitparif now monitors noise throughout the city and oversees noise-reduction efforts.
These noise-reduction efforts in Paris stand to make the city quieter for both people and wildlife. The city’s campaign in the war against noise prompts the question: can we turn down the volume on noise pollution to minimize its impact on birdsong?
Turning down the racket
In 2023, I travelled to Paris to record the songs of the great tit, a familiar European backyard bird closely related to the chickadee.
I used microphones and digital recorders to record birds in the streets, squares and parks throughout the city. I retraced the footsteps of my collaborator, Hans Slabbekoorn, the original biologist who recorded great tits in Paris in 2003.
When we compared background noise with bird songs, we found that great tits sing higher-pitched songs in noisier environments. By singing at a higher pitch, great tits avoid having their songs masked by the low-frequency noise of traffic sounds.
We also analyzed noise data collected across Paris by Bruitparif. We found that Paris is winning the war on noise pollution and the city has grown quieter in recent years. In fact, Paris today is approximately three decibels quieter than it was 10 years ago. Because the decibel scale is logarithmic, a three-decibel drop represents a major reduction in sound intensity.
Despite this progress, great tits in Paris continue to sing at higher pitches than birds in wilderness areas outside the city.
Birds can revert their tune
However, there is reason for optimism. Research has shown that when cities become quieter, birds in other locations have returned to their natural pitch.
The quiet streets during COVID-19 lockdowns provided a rare opportunity to study birds in a quieter world. Biologists in San Francisco found that the urban soundscape became approximately seven decibels quieter during lockdowns — levels rarely observed since the 1950s.
The quiet airwaves allowed birds to change their tune. White-crowned sparrows in San Francisco responded by singing lower-pitched and quieter songs.
Many species of birds benefited from the quiet soundscape of the lockdown period. In a study of 47 species of songbirds in North America, our research team found that species with broad-frequency songs — sounds that are most immune to the impacts of low-frequency noise — expanded their ranges during this quiet period.
These findings reveal that noise pollution affects diverse birds, even those whose songs seem well-suited to noisy environments.
Listening to the future
Our studies in Paris show that a three-decibel reduction is not sufficient to allow birds to return to their natural song frequencies. Further noise-reduction efforts will be required for us to adequately share the airwaves with our feathered friends.
Paris also provides a hopeful lesson about battling noise pollution. Cities can reduce noise by encouraging cycling and quieter transportation. Public policy also plays an important role, exemplified by Paris’s Bruitparif agency.
If we measure noise pollution, we can strive to reduce it, improve our own well-being and create the space for wild birds to communicate at their natural sound frequencies.
Dan Mennill, Professor and Associate Dean of Science, University of Windsor
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This article is republished from The Conversation under a Creative Commons license. Read the original article.
