Did you feel like birds were singing differently during the coronavirus lockdown? If you did, you were probably right.

Thanks to a long-running study of the songs of white-crowned sparrows living in and around the San Francisco Bay area, scientists were able to compare effects before and during the lockdown. What they found came as a bit of a surprise.

Most of the time, it’s male sparrows that sing, and during the silence, the birds improved their vocal performance and sang lower-amplitude “sexier” songs to defend their territory and woo a female. And while it might have seemed to human ears that bird song got louder, the sparrows actually sang more quietly. It’s just that their sweeter, softer songs carried further given the lack of background noise.

“People were right that birds did sound different during the shutdown and they filled the soundscape that we basically abandoned,” said Dr. Elizabeth Derryberry of the department of ecology and evolutionary biology at the University of Tennessee in Knoxville. “As we moved out of the soundscape, the birds moved in and I think this tells us something about just how big an effect we have on birdsong and on communication, especially in cities.”

The results of the study speak volumes to how quickly nature can recover from the effects of human noise pollution.

“This study shows that when you reduce noise pollution there’s almost an immediate effect on wildlife behavior and that’s really exciting because so many things that we do to try to help the environment take a long time to improve.”