This songbird’s beak did a complete ‘Pinocchio’ during and after Covid

The pandemic has had a perceptible impact on the environment, but not always on the same scale. If the rare absence of humans has reduced some pollution of nature, this sudden change has also encouraged more aggressive behavior on the part of invasive species. Then there are cases, like the one involving black-eyed juncos in California, that don’t fit into either category.

In a recent article published in the Proceedings of the National Academy of SciencesScientists reported that during and after the pandemic, black-eyed juncos experienced two rapid evolutionary changes. Specifically, the beaks of small songbirds grew longer during the pandemic, then became stubbier again as human activity resumed, just like in the movie, Pinocchio. But in this case, there was no magic or morality about honesty at stake – just the consequences of human influence on nature.

“We think of evolution as slow because, in general, over evolutionary time it’s slow,” said Pamela Yeh, one of the study’s lead authors and an evolutionary biologist at the University of California, Los Angeles (UCLA). statement. “But it’s amazing to be able to see evolution happening before your eyes and see a clear human effect changing a living population.”

Easier means shorter

Black-eyed juncos typically reside in mountain forests, but in Southern California, climate change has pushed a significant population of the birds toward cities, where they have learned to pick up crumbs and scraps of human food waste. Compared to those of its mountain relatives, the beaks of California juncos evolved to be short and stocky.

“Wild animals have to work hard to find and obtain their food. When humans make the task much easier, the parts of their bodies, like their mouths, that animals use for food adapt,” Yeh explained.

So when the juncos became well established on the UCLA campus, they caught the attention of Yeh and his colleagues, who began a long-term study of the songbirds in 2018. Surprisingly, the birds had gradually evolved a diet “closer to that of an average college student,” said Ellie Diamant, another lead author of the study and an evolutionary biologist at Bard College. The New York Times. So this included “things like cookies, bread… [and] pizza,” she recalls.

Harder means longer

Then the pandemic hit. As classes moved online, the campus became mostly abandoned and trash-free, much to the detriment of the juncos. It was around 2021, about a year after the pandemic began, that Yeh and Diamant noticed a slight change in the junco hatchlings: a longer, thinner beak.

“To be honest, we were quite shocked when we saw how strong this change was,” Diamant recalls. In such a short time, California juncos had essentially “evolved,” such that their beaks had reverted to the shape of their wild counterparts. This change likely increased the birds’ foraging success rate, Diamant added.

But as pandemic restrictions have eased, UCLA students, faculty and staff have returned to campus. Remarkably, as people returned, so did the shape of the juncos’ beaks. As quickly as the beaks had grown, they shrank again in junco chicks born between 2023 and 2024.

“This is remarkable evidence of the rapid ability of these birds to adapt to changes in their environment and food resources,” said Graciela Gómez Nicola, a biologist at the Complutense University of Madrid, who was not involved in the study. Scientific Media Center Spain.

A gray area

Other recent studies have been conducted on how exposure to human activity has amended the morphology of wild animals. But juncos are somewhat different from other urban birds like house sparrows or pigeons, the researchers say. House sparrows and pigeons are “in some way pre-adapted to living with humans” due to their generalist diet, tendency to flock, and ability to nest in human structures.

Juncos, on the other hand, are territorial and generally nest on the ground. So UCLA’s dark-eyed juncos, as common as they may be on campus, represent an ongoing evolutionary mystery, the researchers concluded.

“I don’t feel like we have a lot of success stories when we think about how human behavior affects wildlife,” Yeh said. “I wouldn’t call it a success story yet, but it’s not a disaster story, and it’s not nothing.”