City dwelling male birds in San Francisco likely wish for the pandemic to keep humans in lockdown forever. With people sheltered-in-place and limited traffic noises, male birds can sing their mating calls softer and more soulful. This allows them to improve their vocal range and woo the females with sexier songs. A new study shows that their softer, lower range songs could reach females over greater distances.
Ecological study of male bird mating calls
A behavioral ecologist’s study at the University of Tennessee says various animals adapted to the pandemic’s shutdowns. According to Elizabeth Derryberry, people restricted to their homes have reported awareness of animal sounds becoming more conspicuous in residential areas. Similarly, restricted movement and fewer motorized vehicles made bird songs more audible in the city. Derryberry says it was surprising to see how quickly the birds could adjust to the changed circumstances.
She mentioned that other animals studied at the facility also showed adapted behavior, including coyotes and whales.
Comparisons of mating calls
The study shows that city noise in the mating season dropped by as much as 50%. The numbers of vehicles crossing the Golden Gate Bridge were similar to records dating back to 1954 traffic levels.
The researchers recorded the singing of the white‐crowned sparrows from April through May this year. They compared those recordings with those recorded at the same sites during mating seasons of previous years. The recent recordings indicated that male birds’ repertoires were significantly expanded because they could hit lower notes.
Lower noise pollution benefits sparrows’ love life
Derryberry says the best way to describe the phenomenon is a cocktail party. Arriving early at a friend’s house for a cocktail party allows conversations at normal voice levels. However, as more guests arrive, noise levels increase. This leads to everybody raising their voices and almost shouting.
In reverse, this is how the San Francisco sparrows experienced the pandemic. From having to almost scream their mating calls before the shelter-in-place orders, to melodiously calling females from much further away.
Sexier mating calls
With their sexier sounding songs, male sparrows became better competitors for the girl-birds’ favors who judge the guys by their songs. The volume of their mating songs dropped by almost a third. Interestingly, the researchers found that the sounds of their songs carried about twice as far as before the pandemic.
Consequently, humans became more aware of bird songs than ever before.