Birds exposed to traffic noise as chicks suffer lifelong consequences

An experiment led by Mylene Mariette, a researcher at the Doñana Biological Station (EBD-CSIC), has revealed that birds Exposed to traffic noise during their incubation period and recently emerging from the nest, they suffer negative consequences for the rest of their lives, which would point to similar processes in other species, including humans.

The study, published this Thursday in the journal Science, warns of the need to fight against noise pollution, not only from traffic, but also from noisy machinery used in parks and gardens, where birds usually take refuge in cities.

Although the adverse effects of exposure of animals to traffic noise were already well documented, the effects on physiology, reproduction and development of offspring had barely been studied until now.

To better understand the potential impact, Mariette and her colleagues exposed chicks of a bird species known as the Australian zebra finch to specific acoustic environments: recordings of traffic noise (at levels typical in an urban environment) and of bird calls. birds of his species.

The result, demonstrated through several experiments, was the impact on the health of the specimens exposed to traffic noise, both in the incubation period and the rest of their lives, compared to others raised in the same environment without acoustic stress.

Experiments

First, the scientists exposed the fertilized eggs to similar levels of noise from traffic or the singing of other zebra diamonds (65 decibels in both cases, similar to the level of a conversation) seeing that there was something in the characteristics of traffic noise which, in some cases, caused embryonic death before birth.

The chicks that survived were raised normally by the zebra finch parents.

In a second experiment, they exposed the chicks, without their parents, to noise, isolating them during the night with different types of sound: traffic noise or songs.

“Chicks exposed to noise grew worse and showed more severe signs of cellular damage than those exposed to singing, such as a more rapid shortening of telomeres, which are the protective ends of chromosomes,” explains the EBD-CSIC researcher in a statement.

The negative impact was seen both in pre-hatching noise exposure and in the chick stage, and did not end when noise exposure ended.

Once the chicks left the nest, they were all raised together in an aviary without being exposed to any other recordings.

Long-term consequences

One month after the end of noise exposure, the researchers measured the juveniles again and found that the individuals who suffered traffic noise were no longer smaller than their siblings exposed to singing, but their physiological state had worsened.

A year later, when the chicks were already adult birds, the cellular impact of the noise was still clearly visible.

To find out if the damage persisted over time, the researchers gave the birds the opportunity to breed freely in aviaries, to see who was more successful.

“The results were impressive. “Zebra finches exposed to noise before and after hatching produced only half as many offspring as those that never experienced traffic noise,” Mariette states.

“This was observed in young adults during their first breeding season, but also later in life, in mature adults.”

Researchers still don’t know what makes traffic noise so harmful to chicks, but Mariette says “Whatever the mechanism, an impact of such magnitude on a songbird, which many researchers say cannot hear sounds until a few days after hatching, is very worrying.”

Now it’s time to ask “what impact does noise have on species whose embryos perceive the sound of traffic, including humans, in which fetuses respond to external sounds in the last trimester of gestation”, concludes the researcher.