Birds change their tune amid virus shutdown
This was a silent spring for Northern California residents, as COVID-19 trapped us indoors to wait, worry and whine.
But outside, our birds rediscovered their most sexy serenades. The stage was all theirs.
A first-ever acoustic comparison of avian songs before and during the springtime shutdown reveals that birds respond quickly when humans hush.
They sang more softly — and these songs were faster, with a wider, lower and more romantic range of pitch, according to the study, published in Thursday’s issue of the journal Science.
The sound levels of bird songs fell by more than four decibels during the shutdown; because decibels are measured on a logarithmic scale, songs were about one-third softer. No longer forced to compete with human pandemonium, birds also dropped their pitch by 160 vibrations per second.
“It highlights how much of an effect that humans have on wildlife behavior — and how quickly wildlife can respond when human behavior changes,” said lead researcher Elizabeth Derryberry, an animal communication expert at the University of Tennessee.
“Nature takes over as soon as people get out of the way,” she said.
In April and May, Derryberry was stuck at her Knoxville home with her family, as bored and frustrated as the rest of us.
Then she saw a photo of the near-empty Golden Gate Bridge, with vehicle traffic at levels not seen since 1954 — reversing more than a half-century rise in noise pollution.
“It’s so quiet in San Francisco,” she thought. And wondered: “Are the birds singing differently?” Unable to travel, she enlisted the help of former graduate student Jennifer Phillips, who was doing postdoctoral work at Cal Poly San Luis Obispo.
Phillips quickly packed up acoustic equipment and rushed out to San Francisco, Marin and the East Bay in search of birds perched among the shrubby habitats of lupine, poison oak, sage, and coyote bush.