San Francisco birds started
singing differently in the quiet of the coronavirus lockdown, says a study
in Science.
Before, urban bird
territories were almost three times as loud as rural territories.
However, during the
pandemic, researchers noted that noise levels in urban areas were drastically
lower. In fact, they were consistent with traffic flow in the mid-1950s.
"In other words, the
Covid-19 shutdown created a proverbial silence across the SF Bay Area," researchers
noted.
By analyzing traffic flow
data from the Golden Gate Bridge, researchers found that vehicle crossings from
April to May 2020 returned to levels not seen since 1954. While noise
recordings are not available from the 1950s, researchers said this indicates
that a brief but dramatic change in human behavior effectively erased more than
a half-century of urban noise pollution.
Birds responded by
producing higher performance songs at lower amplitudes, maximizing
communication distance and salience.
"We found that birds sang more softly when noise levels were lower
and at shorter recording distances before and during the shutdown,"
researchers said in the study.
Even though the birds were singing more softly, the study found that
communication distance nearly doubled, elevating species fitness and increasing
mating potential.
"In addition, the signal-to-noise ratio doubled in relative energy,
which helps explain media reports suggesting that bird songs sounded louder
during the shutdown," the researchers said.
From CNN
