Loud, louder, loudest – how birds are adapting to city life

Scientists have discovered that birds in cities sing louder and higher in order to drown out the background noise of cars, building sites, and other sources of commotion. Despite their noisy habitats, you rarely encounter a bird with hearing loss – as they have a key advantage over mammals.

Move to the city and you will likely not need an alarm clock any more – a few blackbirds and starlings in the neighborhood will be more than enough. When they start singing at the crack of dawn, they can reach 90.95 decibels, about the same noise level as a jackhammer.

In cities, birds try to compete with the din from cars, trams, PA announcements, and other noise sources. Behavioral biologists have known for years that birds pit their song against traffic noise by singing more powerfully, and the Max Planck Institute for Ornithology has discovered that Berlin nightingales chirp 14 decibels louder than their country cousins. The volume of their warbling is highest between 5 and 10pm on weekdays, falling to more modest levels at the weekend, when the commuter traffic subsides – just as people adapt their voices to noisy or quiet environments. It came as a surprise to researchers that this “Lombard effect” was also observable in birds; they had assumed that our feathered friends always sang at the top of their lungs.

City-dwelling fowl not only sing louder, they also sing higher. Is this because higher birdsong stands out better against low-frequency street noise? Because it can be heard farther away? Research has shown that higher song only minimally offsets the roar of the streets, and is of no use at all to blackbirds, as they sing much lower than great tits, for example. The higher pitch of birdsong may simply be a side-effect of its volume, and here too, birds behave much as people: if you shout, you involuntarily switch to a higher vocal register – at a loud party, for instance, or on a packed bus. Great tits can even react to changes in the volume of ambient sound in real time; if a truck roars past on the highway, their song becomes especially high and loud.

Although bird protection experts inform us that animals competing against low-frequency noise with higher pitches is not a new phenomenon – it is well-known from birds that live beside raging torrents – they admit they are amazed at how quickly city birds have adapted to noise levels within a couple of generations.

Birds react to noise, but they are more resistant to temporary and permanent hearing loss or damage than people or other animals; the sensory hair cells in their inner ears can renew themselves and thus compensate for heavy noise pollution. “This doesn’t exist in mammals,” says Stefan Launer, Sonova’s resident expert in audiological research and Senior Vice President Audiology and Health Innovation. “These sensors are of interest to researchers as they may offer a kind of template for protecting or regenerating human hearing with the help of biotechnology in the future.”