The song of the city, or how to compete with a highway

'A different kind of bird'. Photo - Ingrid Taylar via Flickr (CC BY 2.0)
City living. Photo: Ingrid Taylar via Flickr (CC BY 2.0)

Stop and listen. What can you hear? The buzzing of a fish tank, the hum of cars, and the soft buzz of your computer or the overhead lights, a rumbling plane, a ticking clock. We live in an age synonymous with the unceasing song of technology. And this hasn’t gone unnoticed by wildlife.

Most man-made noise, from lawn mowers to the groan of industry, occurs at the low-frequency range of the spectrum (<3 kHz). Bird songs are masked when they overlap with this low-frequency urban grumble. To be heard, songbirds are changing their tune.

Singing a different song

Some birds have adapted to their new city life. By changing the frequency of their songs, birds can compete with the urban noise.

Australian Silvereyes not only sing higher and slower in urban habitats compared to rural environments, but they increase the frequency of their calls too.

And it’s not only Australian birds modifying their melodies. European Great Tits sing louder and higher in noisier habitats, while Common Nightingales croon louder when in the midst of heavy traffic. Male American Song Sparrows alter their songs only in the parts being masked by urban noise, singing higher and exerting less energy into singing the lower notes. Urban European Robins have almost sidestepped the issue, singing in the relative hush of the night instead.

Silvereye. Photo: David Jenkins via Flickr (CC BY-NC-SA 2.0).
An urban Silvereye. Photo: David Jenkins via Flickr (CC BY-NC-SA 2.0).

Why do birds sing and call?

Birds learn these melodious songs from a young age for a few main reasons:

  • Simply put, males sing to attract females. Attempting to allure females with the quality and number of their complex musical displays. As women may swoon over a French or British accent, birds sing in different dialects, and this can influence a female’s attraction to a male. Some birds also sing to maintain a bond with their mate.
  • Birds can be highly territorial. To help actively mark and defend territories seasonally or year-round, they sing.

Birds also call to each other to communicate with flock-mates, coordinate flight and to alert others of food or predators.

Basically, birds call and sing to communication with each other. So it’s essential that their message be heard. If a bird’s song is obscured, their ability to entice female interest or keep a territory lessens. Though whether changing their tune impacts a male’s reproductive success has yet to be studied. Singing louder and higher heightens energy and oxygen use in Great Tits, which does negatively  impacting their health.

How do birds change their tune?

Songs are learned, and so can change over time. But calls are innate, developing from begging calls as a chick.

Many species have shown behavioural plasticity, changing their songs under the pressure of the city noise to better suit their surroundings. But Silvereyes have also modified their innate contact calls. This suggests that there may be changes occurring genetically across the generations of city dwellers, or during early development.

The urban-rural divide

The urbanization and industrialization of the world has changed the soundscape phenomenally, creating a novel stage for wildlife. Some have flourished in their new concrete habitats. But not all species adapt, and so can’t persist in an urban backdrop. As such, the diversity and density of songbirds in cities and around highways has diminished relative to quieter rural habitats.

As well as spatial separation, rural and urban birds are becoming more and more vocally distinct as urban birds attune to the city soundtrack. Great Tits from rural environments respond less to urban songsters during territorial invasions than to their rural kin. And the same pattern occurs for urban dwellers.

If urban and rural birds lose the power to communicate, they may not recognise each other as the same species. If they can’t communicate, they can’t breed, and could diverge into different species entirely.

As our cities expand, the world gets busier and noisier. Our metropolitan life shapes not only the way we interact, but how wildlife communicates. Songbirds must adapt, or perish in the urban sprawl of modern life. Luckily, it sounds like some are doing just that.

 

Useful links:

Australian Bird Songs

Common Urban Birds

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Great Tits in the City. Photo: Mezen via Flickr (CC BY 2.0).

 


5 Responses to “The song of the city, or how to compete with a highway”

  1. oselan says:

    Very interesting post Jess, so sad to lose such kind of beautiful birdsong in the future. Good idea to pick this topic. Just wondering if they lose their power to communicate, is it possible to regenerate that ability? For example, by putting them back to their original habitat? Thanks

  2. hartnett says:

    A really interesting post. It’s good news that t least some species of birds are adapting to urbanization and still managing to get their songs heard. Living in the inner city, I sometimes go for days or weeks on end without noticing birdsong, but then a kookaburra call or the beautiful song of magpies will cut into my awareness and stop me in my tracks. I’d hate to think of a world where that never happened.

  3. jrowland says:

    Thanks Asher and Ashton 🙂

    Asher, adapting their communication to the city means that they can can be heard over the city noise. But I couldn’t find any research into how the females responded to the new pitched songs. Being heard over the noise is only useful if, for instance, females are still attracted to the songs, or if it reduces their health/body condition. There are lots of urban bird populations that you could probably classify as thriving, like pigeons, doves, sparrows and miners, which are hyper-abundant, colonising basically every city around the world despite the many issues city life presents, like the noise, the pollution, the diseases etc.

    Ashton, there was a study done where they played city (and country) bird calls to country birds, and vice versa, and they found that the birds responded more strongly to birds from the same habitat type, seeing them as more of a conspecific threat to their territory. So city birds responded more to birds from the city than from the country, and vice versa, suggesting that they are losing their ability to recognise each other.

  4. Ashton Dickerson says:

    I’ve always found this so cool. I wonder if anyone has done a playback experiment using city bird calls to country bird calls. Do you know Jess? I wonder if the songs have changed enough to be unrecognisable to each other.

  5. Asher Trama says:

    Great post Jess! The selection that influences bird song has always interested me. It’s great to know that songbirds have been able to adapt. Though, as you said, this adaptation impacts their health, and as well as diverging from their rural counterparts, is it possible that this adaptation won’t be of benefit in the long run? Or are there stable populations that are not only surviving, but thriving?