The Sound of Evolution

[Image: Istanbul Birds in Flight by Tim O'Brien].

City birds have begun to sing new songs. "Gone is the familiar dawn chorus, with its rich mix of enchanting melodies and calls," New Scientist writes. "In its place is a strangely depleted music – abrupt, high-pitched and sometimes ear-piercing."
It seems that constant background sound in cities is having an alarming effect on bird species.

Some species simply are not able to make themselves heard above the ever-growing racket and are finding themselves squeezed out of the city. Others are beginning to change the way they communicate. In the long term, new species may evolve. If noise levels continue to rise, it seems inevitable that urban bird life will change dramatically.

Birds such as house finches, blackbirds, and – yes – great tits are learning how to adapt.
Researchers found that great tits in the city, for instance, will actually sing "higher-pitched tunes than their forest-dwelling counterpart" – indeed, that city tits even tune in to different noises now because they're drowned out at other frequencies.

[Image: Bird subcommittee on traffic by Rosanne Haaland].

This, too, could have huge implications.

If singing and hearing diverge enough, urban birds may be less likely to find the vocals of rural birds attractive, or even to recognise them as members of the same species. These changes could serve to eventually split populations into genetically distinct urban and rural species. Alternatively, different populations of the same species might adopt differing strategies to cope with urban noise, leading eventually to a species split occurring in birds living in the same neighbourhood.

Roads and other forms of transport infrastructure – such as airports – are a major part of the problem. In Holland, we read, "the construction of a road near a particular [warbler nest] reduced the number of warbler breeding pairs from around 10 to just two. When the road was closed for repairs for two years, five more pairs moved into the area, although the subsequent return of traffic drove them away again."
Everyone, and everything, is just looking for some peace and quiet.
I'm reminded of something I've written for a future issue of Dwell about the role of urban sound control in massive eco-design schemes – but I'll leave that unexplored till the (albeit very brief) article comes out.