Ornithologists and birders reported hearing more bird songs and calls even from the species they had never heard before, but always knew were in the vicinity
Less noise during the lockdown restrictions, which were enforced in various parts of the world to contain the spread of the coronavirus disease (Covid-19) pandemic during this spring, may have allowed birds to sing sweeter and softer songs, according to a study published in the journal Science last week.
The study found that sparrows in the United States of America’s (USA) San Francisco Bay area responded to the new acoustic space during the lockdown in April and May by singing higher performance songs — those involving trills or other vocal ornamentation and at lower amplitudes.
Despite the reduced amplitude, communication distances more than doubled, which could both reduce territorial conflicts and increase mating potential, the study suggested.
Titled Singing in A Silent Spring: Birds respond to a half-century soundscape reversion during the Covid-19 shutdown. The study, led by the Department of Ecology and Evolutionary Biology at the University of Tennessee, USA, also found that the low-frequency noise generated by traffic and vehicle crossings in April and May returned to levels not heard since the 1950s.
Usually, birds that have breeding areas, where ambient noise is high, sing higher amplitude songs. This is called the Lombard effect, an involuntary vocal response to the presence of background noise, because people tend to speak louder in noisy environments.
The study revealed that male birds produce songs with higher minimum frequencies in areas with high energy. While low frequency noise is typical of traffic in urban surroundings.
The study concluded that birds managed to maximise communication and salience. “These findings illustrate that behavioural traits can change rapidly in response to newly favourable conditions, indicating an inherent resilience to longstanding anthropogenic pressures like noise pollution,” it said.
Veteran ornithologist Asad R Rahmani, a former director of the Bombay Natural History Society (BNHS), said he could hear several species, despite living in a crowded part of Lucknow, where there are fewer trees, during the Covid-19-induced lockdown restrictions.
“I live in a crowded area, where there are not too many trees, bushes or shrubs. Nevertheless, during the lockdown when there was no traffic on the streets, I could hear Indian Cuckoo because March to June is its breeding season so it is very vocal, Greater Coucal, Laughing Dove, Jungle Babbler, Golden Oriole, Peafowl, Brown Rock Chat, Rose-ringed Parakeet, House Sparrow, Spotted Owlet, Indian Scops Owl (both at night), Brown-headed Barbet, Coppersmith Barbet, Black-rumped Flameback (woodpecker), Red-vented Bulbul, Common Iora, and a few other species of birds,” Rahmani said.