7 June 2012

Birds Sing a Different Song In The City

urban sparrow
Urban birds sing short, fast and high pitched songs. Their rural cousins sing mellower traditional tunes.

How strange that scientific research seems to be corroborating stereotypical differences between town and country. Throughout history a distinction has been made between the quick and cheeky urbanite and the slow conventional country bumpkin.

I am reminded of Timmy Willie.

In the Tale of Johnny Town-mouse Beatrix Potter has country mouse Timmy Willie, born in a garden (I doubt she was thinking of my kind of garden), being accidentally taken to the city were house mouse, Johnny lives. Timmy is overwhelmed by the noise of carts, people running about, and ‘boys whistling in the streets’. Where he lived there was ‘no noise except the birds and bees, and the lambs in the meadows’. Johnny and his family are depicted as squeaking, tumbling, laughing, racketing about, and being bold. In contrast when Potter draws Timmy he is nearly always sitting quietly. His greatest pleasure is sitting in his burrow watching birds, and sniffing the smell of violets and spring grass.

It appears the differences between their behaviours can be explained as a response to their environment.

And such seems the case when the songs of birds in cities and nearby forests are analysed. Many research projects are finding those in noisier locations sing with a higher minimum frequency and use fewer common song patterns. One report calls them ‘hurried’ songs. The reasonable explanation for this distinction is that in trying to defend their territories and attract mates male birds have to sing higher and louder to overcome the hum of man-made noise. Lower frequency notes are drowned out and the message of ‘here I am’ is not heard.

Lower sounds also travel further. It is suggested that because an urban environment is more open than natural woodland birds can see each other easier, which reduces the need to sing long, lower songs. I doubt the naturalists are implying urban birds are over-populated and so close to each other they are becoming more visually orientated. I think it is a matter of having smaller territories: gardens and parks instead of woods and fields.

As we know, different songs mean different cultures. It has been found that Great Tits respond less to songs that are different from their own. Also this cultural difference is apparent within a distance of even a mile. A problem then arises that birds of the same species but from different local environments may not be able to communicate.

When fully fledged male Great Tits move away from their home area up to a distance of 2 miles, but if they sing a slightly different song pattern and pitch from resident birds could that mean they will have trouble attracting females and establishing territories?

What implication does this have on the species as a whole? There is a possibility that the distinction between urban and rural populations becomes so extreme evolutionary forces will create different species, or phenotypes (observable characteristics, shaped by inheritance and environment) at least.

Research has already shown birds that have a natural low frequency voice but do not possess the ability to adapt are being found less frequently in noisy areas such as towns and along motorways.
A thought I have on this is, if the constant low hum of people and cars is driving out birds species that cannot adapt, what does it say of pied wagtails who thrive in the most unnatural and loud environment of car parks?

A report by Aberwystwyth University asks “are nature reserves in noisy areas ecological cages rather than source populations from which residents are able to disperse?”

Johnny Town-mouse paid a visit to Timmy Willy but was unnerved by unfamiliar sounds and the overall quiet. He left for home in the very next hamper.

Beatrix Potter Johnny Town Mouse

Sparrow image from Telegraph