During the COVID-19 pandemic lockdowns in 2020, humans stayed inside. This period was called the ‘anthropause period.’ This gave researchers an opportunity to study the behaviour of urban (city) birds when humans were not around.
During the anthropause, in cities, there were fewer people, fewer vehicles, less pollution, and less noise. In a study published in the Science journal in September 2020 by researchers in the Department of Ecology and Evolutionary Biology at the University of Tennessee in America, it was found that White-Crowned Sparrows (Zonotrichia leucophrys) changed their songs – with less noise to compete with, their songs became louder.
When lockdown finished, researchers were interested in how birds behaved when humans resumed their usual acitivities.
Researchers from the Department of Ecology and Evolutionary Biology at the University of California in Los Angeles, America; the Faculty of Biological and Environmental Sciences at the University of Helsinki in Finland; and the Sante Fe Institute in New Mexico, America, wanted to study bird behaviour and how they reacted with fewer humans in the city.
The researchers focused on the behaviour called ‘the fear response’ – whether the city birds changed their attitude towards humans and became more fearful or braver.
Between 2017 and March 2020, they collected bird behaviour information in three cities compared with rural birds. For 18-months when the university was closed, the researchers conducted human pedestrian studies.
They measured the flight initiation distance (FID) for 404 individual city birds and for the collective population before, during, and after the anthropause to examine if birds experienced longer-term changes after 18-months of lower human activity in their area. The FID measured the time taken for a bird to fly away when a researcher walked at a steady pace towards it. It also measured the distance it moved to.
The researchers studied the Dark-Eyed Junco (Junco hyemalis), a songbird native to North America, that began breeding in southern Californian cities during the past 20-40 years.
The researchers expected that the Juncos would become braver during anthropause and more fearful when humans became more active in the cities again.
However, the researchers found that the Dark-Eyed Juncos, at the individual level and population level, did not change their fear levels during the anthropause phase. The birds changed their use of space during anthropause, traveling further afield than usual. The Juncos also had more babies.
Interestingly, the birds became significantly braver afterwards, when humans resumed usual activity. After the anthropause period, the Juncos took longer to fly away when a human approached, and did not hop or fly very far, often soon flying back to their original position. More information is expected to be gathered for a longer-term study.
Photographer: Michael Catalano
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Diamant ES, MacGregor-Fors I, Blumstein DT, Yeh PJ. 2023 Urban birds become less fearful following COVID-19 reopenings. Proc. R. Soc. B 290: 20231338. https://doi.org/10.1098/rspb.2023.1338
Derryberry EP, Phillips JN, Derryberry GE, Blum MJ, Luther D. 2020 Singing in a silent spring: birds respond to a half-century soundscape reversion during the COVID-19 shutdown. Science 370, 575–579. (doi:10.1126/science.abd5777)