San Francisco sparrows sang more quietly and 'chilled out' in coronavirus lockdown
Sparrows in North America sang more quietly and were generally "chilled out" as the background noise of cities dropped during the coronavirus lockdowns, according to a new study.
Researchers said the song of white-crowned sparrows in San Francisco had recovered the acoustic quality of the 1970s as traffic levels and other sources of noise decreased during the pandemic.
White-crowned sparrows had seen the quality of their mating calls decline in cities over the decades, with increasing noise pollution levels forcing males to sing louder and less effective songs in order to make themselves heard above the din. But a study published in Science magazine suggests that the sparrows' songs became around 30 per cent softer during Covid-19, and the calls were also of a higher acoustic quality.
The study suggested that the combination of less background noise and higher quality song meant the birds could probably hear each other from double the distance they could previously, helping attract females and avoid rival males.
According to the study by behavioural ecologists Elizabeth Derryberry, from the University of Tennessee, and Jenny Phillips, from California Polytechnic State University, the changes to the songs are likely to have reduced the level of conflict between urban male sparrows.
"I think that the aggression levels might have gone down so that everybody chilled out,” Professor Derryberry told Science magazine.
The pair, who have been studying the species in and around San Francisco for more than two decades, said the recent bird song heard compared favourably with recordings made of white-crowned sparrows in the 1970s.
The experts explained that research has found birds who are forced to sing louder to compete with a noisy environment can often age faster because of the added stress to their systems. The noise can also make it harder for birds to hear their own chicks, and may contribute to decreased levels of bird diversity in many cities.
However, with traffic and other activity returning to cities, researchers said that they plan to monitor the sparrows when they begin their springtime serenades next year to see if their songs have changed in quality once more.
