The noise of the cities forces the birds to increase the power of their song or to change to higher tones to make themselves heard among their peers, according to a study published by the scientific journal Behavioral Ecology.
The study, prepared by the researcher of the National Museum of Natural Sciences and president of the Scientific Committee of SEO / BirdLife, Mario Díaz, reveals that each species of bird modifies its behavior depending on its abilities but, in general, noise and compensation of its effects have negative consequences.
"In the same way that exposure to excessive noise can harm people, noise pollution harms birds," says the researcher, who advocates a "naturalization of the city", with a higher percentage of green spaces that screen against noise.
A sharper song
According to Mario Díaz, the background noise of the city moves in low or serious frequencies and that is why some birds choose to emit a higher song to make themselves heard, such as the male chickadee or the tit, with negative consequences in communication with the female.
On the other hand, to survive in a city some species only sing when there is less noise, such as the urban robin, which prefers to do it at night, while others get up early or advance the mating phase.
Make yourself heard
If the two previous options are not possible, adds this scientist, the bird chooses to sing more and at a higher volume to make itself heard, a behavior modification that can attract not only potential mates, but also its predators.
In his study, Mario Díaz points out that at a noise level above 70 decibels the birds give up and choose to sing less - which indicates that the benefits of singing do not outweigh its costs - and in other cases they decide to leave the place .
In fact, "various studies have shown non-random losses of species, especially those that sing at low frequencies, in the vicinity of noise sources, such as highways or oil or gas pumping stations", indicates the researcher.