In fact, do urban birds speak the same language as the birds in the country? Do they share the same dialect?
Town and country: two different worlds of sound
In nature, dense plant life absorbs high frequencies. To communicate, birds tend to use lower-pitched sounds, which pierce forest growth and are more easily perceived by others. Since time immemorial, birds have adapted to this audio reality.
In town, the situation is different. Cars, trucks and other motors emit mostly bass-frequency sounds. Moreover, architecture reflects and distorts high-pitch sounds.
A country bird that moves to town has to adapt to the new environment and the new reality. The noisier the environment, the louder it has to sing.
How do you make yourself heard in town?
For birds, sound is primordial. Songs and calls govern pair formation, provide information about the owners of the site or signal the presence of a predator. In an urban environment, the omnipresence of bass frequencies to a certain extent obscures bird song, and the message is no longer transmitted as effectively. Some species will not sing until the background noise is weaker, and therefore avoid singing in the morning and evening: they wait for rush hour to be over. In fact, if American robins sing at night, it’s to make themselves heard by avoiding the ambient daytime noises, and not because of the presence of artificial light.
Most of the other species modify their song. Some of them emit higher-pitched sounds that pierce the noises of the city. The more noise there is, the higher-pitched the white-crowned sparrow’s song gets.
Sometimes only certain parts of the song are modified. In the city, the red-winged blackbird modifies the initial trills of its song: changes that are detrimental to recognition and understanding of the message. In taking a few syllables away from its song, the blackbird sings for less time, and its message risks going unnoticed or being misunderstood. An equally amazing fact: birds, like humans, sing faster in town than in the country!
Are we seeing the formation of new species?
Urban birds no longer sing the way their country colleagues do. As years go by, it becomes more and more difficult for a rural bird to understand what its urban counterpart is saying. With birds, reproduction is linked to communication. Radical modifications to their song will produce communication problems and could give rise, in the long run, to the emergence of new species that are anthropogenic in origin, meaning resulting from modification of the environment by human activity.