By Taylor Nicioli, CNN
(CNN) — Dark-eyed junco songbirds have been serenading the University of California, Los Angeles campus for decades as they forage for food.
The species from the sparrow family is not usually found in cities. But as the climate crisis affected their mountain forest habitats, they started taking up residence in Southern California’s more urban settings, including colleges such as UCLA.
The city-dwelling birds have shorter and stubbier beaks, a stark contrast from the long ones their mountain counterparts use to eat seeds and insects.
However, as UCLA researchers looked over data on the birds that have resided on their campus in recent years, they noticed something odd: Juncos that hatched in 2021 and 2022, after the start of the Covid-19 pandemic, had longer beaks similar to those seen on the mountain birds. But as pandemic restrictions eased at UCLA and students returned to classes, the city bird traits returned, and the beaks of the birds hatched in 2023 and 2024 were shortened once more, researchers Pamela Yeh and Eleanor Diamant reported in December in the journal Proceedings of the National Academy of Sciences.
“We often think about evolution as a slow process,” said Diamant, the study’s lead author who was a doctoral student at UCLA during the research and is now a visiting assistant professor at Bard College in Annandale-on-Hudson, New York.
“We thought that this would probably be too short of time to see a change in the population. … So we were really surprised when we ran the data,” Diamant added. “When I did the year-by-year comparison, it was remarkable how stark the change was.”
The authors hypothesize that, compared with the longer-beaked mountain-dwelling birds, the shorter beaks on campus birds might be better suited for a wider range diet of human food scraps. But in 2020, when classes first went online and dining halls closed, the beaks of newborn birds evolved back to their longer state fitted for their natural diets.
The study highlights the effects humans can have on wildlife and shows how fast evolution can occur for animals needing to adapt to their surroundings, the researchers said.
Humans and nature are “really quite interconnected, and we’re very much a part of the ecosystem. I think that’s the first takeaway,” said Yeh, the study coauthor and a professor of ecology and evolutionary biology at UCLA. Yeh has researched the juncos for about three decades.
“I think the second takeaway is how much there is right in our backyards,” Yeh added. “I bet that there’s a lot of evolution happening, rapid evolution, that we can see right before our eyes that we don’t even know about because we’re not looking carefully enough.”
Rapid evolution songbirds
Charles Darwin famously encountered evidence for his theory of evolution in 1835 when he noticed that finches in the Galápagos off the coast of Ecuador had varying beak shapes suited to their food sources on the differing islands. Later, in the 1970s, the finches on these islands were observed experiencing rapid evolution brought about by drought. During a drought, birds with larger beaks were more successful at survival, as they were able to eat the harder seeds found on the dry ground. Natural selection, the process by which advantageous traits are passed down, resulted in the next generation having larger beaks.
Yeh and Diamant also pointed to more recent research in which birds have been observed to change beak shapes, such as a 2017 study on