14Birds, bugs and the city's wild soundscape

The short version: City birds change their songs to be heard over traffic: studies have found great tits singing higher in noisy parts of Leiden, nightingales singing louder in Berlin traffic, and robins singing at night where daytime noise is high. Insects can rival machines, and the 2024 periodical cicada emergence was reported at 90-100 dB, though the reports gave no distances. Cities and nonprofits now map and protect quiet places, from EU "quiet areas" to certified quiet parks. The 2020 lockdowns showed how much of the background is human: seismometers worldwide recorded up to 50% less high-frequency ground noise, and 11 public sites in London averaged 5.4 dB LAeq quieter than a year earlier.

Why do birds start singing so early in the city?

What you hear: A wall of birdsong before sunrise, sometimes well before.

The dawn chorus is the burst of birdsong around first light. Urban birds can start it earlier than rural birds: in a Leiden University study, urban great tits began singing an average of 22 minutes earlier than rural ones. The same work cites research linking airport noise to earlier dawn choruses (Gil et al., 2015), which suggests birds may be getting their songs in before the morning noise begins.²⁶⁰

Light plays a part too. The Max Planck Society reports that near streetlights, early singers such as blackbirds and robins start earlier, drawing on a study in a forest near Vienna, and that blue tit males started about 15-20 minutes earlier.²⁶¹

Do birds sing higher in cities?

What you hear: A familiar song that sounds slightly thinner or more piping on a busy street than in the woods.

In 2003, H. Slabbekoorn and M. Peet reported in Nature that great tits in noisier territories in Leiden, the Netherlands, sang with a higher minimum frequency. They read this as a learned, flexible adjustment.²⁶² Traffic noise is concentrated in the low frequencies, so moving the bottom of a song upward keeps it from being masked.

The trick works better for some species than others. The Max Planck Society notes that raising pitch helps great tits more than blackbirds, which sing lower.²⁶¹

Do birds sing louder in noisy places?

What you hear: A nightingale that seems to be shouting over the morning commute.

Henrik Brumm recorded 15 male nightingales in Berlin on weekday mornings (about 5-10 a.m.) in spring 2001 and 2002, published in the Journal of Animal Ecology in 2004. Males in noisier territories sang louder, with about 14 dB between the quietest and loudest. Three birds recorded on weekends sang more softly when traffic dropped.²⁶³ Berlin has about 1,500 nightingale breeding pairs, and in aviary tests nightingales sang more forcefully under white noise.²⁶¹

Since decibels are logarithmic, a 14 dB difference is a large one: roughly 25 times the sound energy.

Why is a bird singing at 3 a.m.?

What you hear: A full, melodic song in the dark, often from a tree near a streetlight.

In 2007, R. A. Fuller, P. H. Warren and K. J. Gaston published "Daytime noise predicts nocturnal singing in urban robins" in Biology Letters. They found that daytime noise explained more of the variation in night singing among urban robins than night light did.²⁶⁰ Press coverage of the University of Sheffield work at the time reported noise levels 10 times higher in places where birds were singing at night.²⁶⁴

So the streetlight is not the whole story. The likelier explanation from this study is that robins in loud places move their singing to the hours when the city is quiet enough to be heard.

How loud are cicadas?

What you hear: A pulsing, electric drone from the trees that can drown out conversation.

In 2024, periodical cicada Broods XIII (on a 17-year cycle) and XIX (13-year) emerged together for the first time in 221 years, overlapping in parts of Illinois and Indiana.²⁶⁵ Researchers expected the overlap zone to be small and around Springfield, Illinois, and Gene Kritsky estimated up to about 1.5 million cicadas per acre in the Northern Illinois Brood (XIII).²⁶⁶

NBC Chicago reported that the CDC cites meter and phone-app readings of 90-100 dB for cicadas, "well above" the 85 dB recommended exposure limit.²⁶⁶ The American Academy of Audiology cited reports of 105 dB in clusters of about 1,000 insects, but added that choruses "may not be loud enough to cause a temporary threshold shift."²⁶⁵ None of these reports gave a measurement distance or weighting, so treat them as rough field readings, not exposure levels you can compare with a workplace limit.

Distance changes the picture. In a 2021 explainer, the National Institute for Occupational Safety and Health (NIOSH) said cicada noise measured 3 feet from a heavily infested tree "may approach 100 dBA," and estimated about 94 dBA at 6 feet, 88 dBA at 12 feet and 82 dBA at 24 feet - a drop of 6 dB with each doubling of distance. Those distance figures are estimates, not field measurements.²⁶⁷

Where can you find quiet in a city?

What you hear: Wind, leaves, your own footsteps - and the absence of traffic.

Noise policy has started protecting quiet as well as limiting noise. How quiet is defined and measured is covered in Measuring and finding quiet.

• EU quiet areas. The EU's Environmental Noise Directive lets cities designate and protect quiet areas.²⁶⁸
• Hush City. A citizen-science app developed by Antonella Radicchi at TU Berlin, it lets residents map places they find peaceful. Berlin and Limerick, Ireland have used it for quiet-area planning.²⁶⁹ Limerick asked the public to use it from early 2020, during its year as European Green Leaf city.²⁶⁸
• Quiet Parks International. Co-founded by Gordon Hempton and Vikram Chauhan, it certifies quiet places. Its first Wilderness Quiet Park is the Zabalo River in Ecuador, and its first Urban Quiet Park is Yangmingshan National Park in Taipei, awarded in June 2020.²⁶⁹

The reason for the effort: as reported by Euronews from European Environment Agency figures, 1 in 5 Europeans is exposed to harmful noise, linked to about 12,000 premature deaths a year and 6.5 million people with chronic sleep disturbance.²⁶⁹ What the health agencies say about noise is in What noise does to you.

In the US, the National Park Service's Natural Sounds and Night Skies Division collects baseline data on ambient sound in parks, identifies noise sources and ways to reduce them, and runs an overflights program covering air tours, airspace design and military flights.²⁷⁰

Did cities really get quieter during the 2020 lockdowns?

What you hear (in spring 2020): Birdsong you had never noticed, and a street you could hear across.

Yes, measurably. Scientists sometimes call the period the anthropause. In a July 2020 Science paper, Lecocq, Hicks, Van Noten and colleagues reported a global drop in high-frequency seismic noise - ground vibration from traffic, industry and people moving around - of up to 50%, lasting months. They called it the longest and most prominent reduction on record. It was strongest in populated areas and closely tracked human mobility data.²⁷¹

At ear level, Aletta and colleagues at University College London compared 11 public sites in London in spring 2019 and spring 2020. Average sound levels fell by 5.4 dB LAeq, ranging from 1.2 dB to 10.7 dB depending on the site.²⁷² The size of the drop depended on what normally dominated each spot: places loud with traffic behaved differently from places loud with people.

Note the two measures. The seismic figure is a percentage drop in ground vibration; the London figure is a change in A-weighted airborne sound. Both point the same way, but they are not the same quantity.

In the US, a study of white-crowned sparrows in the San Francisco Bay Area, led by Elizabeth Derryberry of the University of Tennessee, Knoxville, was published in Science in September 2020 as "Singing in a Silent Spring." According to the university, shutdown traffic on the Golden Gate Bridge compared with levels from 1954, and urban San Francisco was no louder than the surrounding rural county. The sparrows sang more softly, but their songs carried about twice as far.²⁷³

In Boston

We found no Boston-specific measurements of the dawn chorus, urban bird song changes, cicada levels, lockdown sound levels or quiet-area mapping. The studies above come from the Netherlands, Germany, Austria, the UK, Illinois and San Francisco. The mechanisms they describe - songs pushed higher, louder or later by traffic noise, and quiet that returns when traffic stops - are general, but how strong they are in any given city has to be measured there.

Elsewhere in the world

Most of the urban birdsong research cited here is European: Leiden for great tits, Berlin for nightingales, the UK for robins, and the Vienna area for the streetlight effect.^262263260261 The EU is also the only jurisdiction here with a legal basis for protecting urban quiet areas, while the first certified Urban Quiet Park is in Taipei.²⁶⁸²⁶⁹

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