Some birds born during the period of restrictions linked to the covid-19 pandemic are present a different beak shape and size compared to those who did so before and after the pause in human activity.
This is the main conclusion of a study carried out by researchers at the University of California, Los Angeles, USA, who followed hundreds of black-eyed juncos (Junco hyemalis).
The analysis was carried out on specimens born on the campus of the aforementioned university. before, during and after the “anthropause”this period which took place during the pandemic during which human activity and therefore waste production was reduced.
Previously, we had already observed that urban animal populations adapt to the dietary and behavioral niche of busy cities by humans. For example, it was known that the shape and size of reed beaks differ in Los Angeles compared to local wilderness areas: reeds in cities have shorter, thicker beaks.
This change may be due to the exploitation of food waste, which leads to changes in its shape and size.
Tracking tip size and shape
To further understand these differences, the team led by Eleanor S. Diamant and Pamela J. Yeh set out to track the size and shape of the beaks of these birds at different time periods, taking into account that The sharp decline in human activity from March 2020 provided a unique opportunity for exploration.
Before Covid-19 restrictions, researchers observed that urban juncos had beaks of a different size and shape from those of wild birds.
However, Birds born in Los Angeles during the ‘anthropause’ showed a wild shape to their beaks. In the years since restrictions were lifted, reed peaks have returned to their pre-pandemic urban form, they conclude.
The Covid restrictions constituted “a natural experiment” to examine the impact of human activity on wildlife, write the scientists in their article published this Monday in the journal PNAS.
In just a few years, urban juncos rapidly changed their morphology and those that hatched during and shortly after the “anthropopause” exhibited non-urban phenotypes. Despite this, the return of human activity causes a rapid return to the morphology associated with the city.
“These results show the how quickly and intensely humans can affect other species (…). “Our work highlights the need to understand the complex interactions between the two.”
The cause is unclear
The cause of the rapid change in bill morphology remains unclear. Even if, according to the authors, the results suggest “a high adaptive sensitivity” in an urban bird population during the cessation and resumption of human activity.
Together, they speculate that food waste could drive the adaptive evolution of a more general beak shape in urban juncos, which changes rapidly in response to changes in resources.
Future research should determine how bill shape varies depending on foragingadaptation and genetics in reeds, they emphasize.
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