Reacción a "The absence of human activity during pandemic lockdowns altered the peaks of a bird species"

This scientific study invites us to reflect on how humans can influence the species that share the urban environment with us. The authors took advantage of the drastic reduction in human activity in the city of Los Angeles during the COVID-19 restrictions, known as the “anthropause”, to analyse changes in the morphology of the beaks of the dark-eyed junco, a species of passerine bird that is very common in North America. Using a robust research design, they compared the dimensions of the beaks of these birds in the city and in nearby natural areas at three key moments: before the pause, during lockdown and after the return to normal activity.

The researchers observed that juncos born and raised during 2020 and 2021, i.e. during the period of reduced human presence in the city, had beak dimensions that differed from those of their relatives born before or after the “anthropause” and were very similar to those of their wild counterparts. This change was apparently related to a significant decrease in their main food source, the organic waste available in the city. This forced the birds to change their diet, seeking more natural food and accessing green areas of the city that previously had a greater human presence. The beak is an essential tool for eating, so a change in diet may have favoured a beak shape more suited to this new type of food.

This study is one of the first to document a morphological change in urban birds in response to the “anthropause”. It is remarkable evidence of these birds' rapid ability to adapt to changes in their environment and food resources. The authors are cautious and do not rule out the influence of other factors, such as phenotypic plasticity, genetic variation or the migration of non-urban reed warblers to the city during lockdown. The findings are highly suggestive and represent an interesting contribution to ecology and evolution in urban environments, an emerging discipline that reminds us in this case how waste generation and the occupation of urban spaces influence biodiversity.