Pandemic restrictions have changed a Los Angeles bird’s beak

“Yes, you can say we saw the evolution live,” Ellie Diamant, of Bard College and co-author of the study published Monday in the journal PNAS, told this newspaper. Diamant and her colleague Pamela Yeh, of the University of California, Los Angeles (UCLA), observed how a small bird very common in urban areas of Los Angeles, the black-eyed junco, changed the shape of its beak to more closely resemble that of its wild counterparts during the year and a half that the city slowed down due to the Covid-19 pandemic. Once people returned to their usual rhythm of life, the urban reed once again displayed its characteristic peak. The authors argue that this change was mainly due to an adaptation to available food, since human waste decreased.

“Black-eyed juncos are one of the most common birds in North America. They are quite remarkable because they feed on the ground and emit a distinctive song. In Southern California cities, they have occupied college campuses and large urban parks because of their large green spaces, favorable for their breeding conditions. But they have also reached even more urbanized areas, for example in Hollywood, and are now expanding toward the center of the city,” says Yeh.

The birds that inhabit the UCLA campus, which are the ones studied by the authors, have shorter, thicker bills than those in the forest populations, which are thin and long. The former feed mainly on waste that people throw on the ground or place in trash cans and containers. During this time, wild species feed on seeds, insects and other natural resources.

During the “anthropause” (the period in which human activity significantly decreased due to the pandemic, which lasted between a year and a half and two years in Los Angeles), “restaurants were closed and humans were absent, so birds that relied on urban food couldn’t eat as much or as well, unlike those that were better at exploiting seeds,” notes Diamant. “Birds whose beaks are associated with urban environments were therefore probably not in good condition to successfully reproduce and raise their offspring,” he continues. In contrast, birds with long, thin beaks “were better able to exploit seeds and insects, and therefore reproduce more efficiently.” After the anthropause, these selection pressures changed again.

For Yeh, what was most surprising was how quickly the juncos changed – in just two generations, with birds born in 2021 and 2022 – and how strong that change was in their morphology. “It seems very likely that we can call this an evolution,” he says. “We cannot rule out the possibility that plasticity, such as birds tapping less on concrete during the pandemic due to the lack of human food in these areas of campus, or other non-evolutionary effects, may have played a role. However, the pattern we observe appears to demonstrate differences in the physical condition of the parents rather than the environment in which the chicks are raised,” he adds.

less fearful

The researchers also recorded changes in the behavior of the reeds. For example, the fear response toward humans was reduced after anthropause, even in the same individuals. They also became less aggressive on the break. You wouldn’t be surprised if other animal species, including mammals, experienced similar changes before and after the pandemic. “We don’t know, but I think this study shows how interconnected we are with our non-human neighbors and how, in some cases, they can respond quickly to our collective behavior,” he concludes.

Can we speak of a round-trip evolution? Changes that occur and then are rejected because they are no longer beneficial? “Yes, it is likely that this happened,” says the researcher. “It seems like what was beneficial changed quickly. Birds born shortly after the pandemic primarily exhibited the trait associated with the city. “This is because these features are likely more effective in typical urban conditions, but not in conditions without human activity,” he says.

The marriage granted

This is not the first time that scientists have observed evolution live. The biologist couple Rosemary and Peter Grant demonstrated that a new species can appear in two generations. “The Grants and their team discovered rapid evolution in the Galapagos several decades ago, when extreme drought then heavy rain selected for larger, then smaller, peaks,” the scientist recalls.

Diamant believes that the “father” of evolution “would be surprised and delighted” if he saw these urban birds of Los Angeles: “Darwin viewed evolution as a slow and essentially gradual process. In fact, all the diversity we see in the world has taken a long time to evolve, he points out.