Paris birds still sing too high despite quieter city

Whenever I walk through Paris with a microphone in hand, my ear is split between two worlds: the steady rumble of traffic, and those tiny perched voices that keep singing right over the top of it. A study published in 2026 in the scientific journal Ornithological Applications has now put precise numbers on what many city dwellers had long suspected: in Paris, great tits sing higher than their country cousins. And they keep doing so even after a decade of serious efforts to bring noise pollution down.

Twenty years between two field recordings

The story behind this research feels almost cinematic for anyone who loves field recording. In 2003, Dutch biologist Hans Slabbekoorn, from Leiden University, walked through Paris with a Sennheiser ME67/K6 shotgun microphone and a cassette recorder, capturing the songs of great tits (Parus major) in the heart of the city as well as in the surrounding forests. Twenty years later, his Canadian colleague Daniel J. Mennill, from the University of Windsor, retraced the exact same path, with the same microphone model, but on a digital rig this time (Zoom F3, 48 kHz, 32-bit). The goal: to rigorously compare two eras and see whether the measurable drop in urban noise had let the birds reclaim their original voice.

Three decibels less, so what?

Paris has made progress. According to data from Bruitparif, the official noise observatory for the Paris region, the city is roughly three decibels quieter today than it was a decade ago. Because the decibel scale is logarithmic, that's not a trivial gain: three fewer decibels means roughly half the sound energy. Several levers explain the improvement: more cycling, the rise of electric vehicles, quieter road surfaces, lower speed limits, and the noise radars I covered in an earlier post on sound radars and urban noise pollution.

The great tits, however, haven't budged

And yet, the figures are stubborn. In 2023, urban great tits in Paris sang at an average minimum frequency of 3,535 Hz, against 3,256 Hz for their forest neighbors just outside the city. That's nearly 280 Hz of difference. More striking still: those values are almost identical to the 2003 measurements (3,428 Hz in town versus 3,460 Hz in the forest). In short, the city has grown calmer, but not calm enough for the birds to lower their voices. The acoustic reflex, built up over generations, is resisting the modest lull.

Why sing high in the city?

The logic is purely physical. Road noise is dominated by low frequencies, which travel far and mask anything in their spectral neighborhood. For a male to be heard by a female or a rival, he has every reason to climb above that noisy zone. This is what biologists call vocal plasticity: birds adjust their output to the surrounding soundscape. The phenomenon has been described in blackbirds, robins, white-crowned sparrows in the United States, and Asian great tits in Seoul. Paris is just one case among many, but with one rare scientific advantage: a clean before-and-after dataset spanning twenty years.

A lull that still isn't enough

During the 2020 lockdowns, several research teams observed that some birds took advantage of the unusual quiet to sing lower and softer. In San Francisco, white-crowned sparrows reverted to an almost rural voice within weeks. In Paris, the gradual three-decibel drop spread over ten years did not produce the same effect, probably because it remains too modest, and because the noise threshold below which birds can genuinely relax their vocal effort has not yet been crossed. To preserve acoustic communication for urban wildlife, we'll need to go further: fewer combustion engines, more sound-absorbing surfaces, and likely a rethinking of certain major arteries.

Soundscape as living heritage

This study resonates with me, because it ties together two things I love putting forward: the rigor of ecoacoustics and the awareness that a soundscape is also a living habitat. It's exactly the lens used in my earlier piece on geophony, biophony, and anthropophony, where the dominance of human-made sounds keeps drowning out animal voices. The song of a Parisian great tit in 2026 is both ecological data and cultural testimony. And while our human ears tend to grow used to the racket, our feathered neighbors don't have the luxury of forgetting.

If you live in a city: do you also pick up that higher edge in the great tit's song, or do human sounds drown them out completely where you are?