Some urban birds modify their songs to make themselves heard amidst the noise and chaos of cities. Sometimes the changes are so great that some of them are unable to communicate with individuals of the same species. These are the results of a study carried out over eight years with different passerine birds in Spain and Brazil.
In some species, singing is essential to defend their territory and attract a mate. However, in an environment with great environmental noise such as cities, they must use another range of frequencies to get their peers to hear them. The separation is so great that an urban bird may not be able to communicate with a field bird, despite being of the same species. “We call this cultural mutation, which is faster than genetic mutation,” says Salvador Peris, director of the research, “and results in fragmentation of populations.”
Among other things, the researchers also studied the populations of birds that lived on roads with different levels of traffic, verifying that the presence of some species declines on those with the most traffic. This is the case of trans-Saharan migrant birds, which, having much more complex song repertoires, would be more affected by environmental noise.
The effects of noise pollution are not only important for the conservation of birds, they also offer a panorama of the “cultural evolution” in their song. This aspect can change very quickly in a few generations, especially in those species with a greater capacity for learning new songs. This is the case of the nightingale, of which up to 110 different melodies are known.
