Dark-eyed junco songbirds on the University of California, Los Angeles (UCLA) campus have shown rapid beak evolution in response to human activity. This species, typically found in mountain forests, established residence in urban areas like UCLA due to climate crisis effects on their natural habitats. Urban juncos generally possess shorter, stubbier beaks, which are believed to be better adapted for consuming human food scraps, contrasting with the longer beaks of their mountain counterparts used for seeds and insects.
UCLA researchers Pamela Yeh and Eleanor Diamant observed a significant change in beak length among juncos hatched during the COVID-19 pandemic. Birds hatched in 2021 and 2022, when pandemic restrictions led to reduced campus activity and dining hall closures, developed longer beaks, similar to mountain-dwelling juncos and adapted for natural diets. As campus activities resumed in 2023 and 2024, the beaks of newly hatched birds shortened again, reverting to urban-adapted traits. This rapid evolutionary shift was reported in the journal Proceedings of the National Academy of Sciences in December.
Research Findings and Implications
- Rapid Evolution: The study highlights how quickly evolution can occur, with noticeable changes appearing within just a couple of generations.
- Human Impact: It demonstrates the direct influence of human activities, even transient ones like campus closures, on wildlife adaptation.
- Dietary Adaptation: Researchers hypothesize that shorter beaks are advantageous for a diverse urban diet including human food scraps, while longer beaks are suited for natural diets.
- Comparison to Other Studies: This observation aligns with historical evidence of rapid evolution, such as Darwin's finches and more recent studies on great tits and hummingbirds changing beak shapes in response to bird feeders.
- Future Research: While evolution is the primary hypothesis, researchers are working to obtain genetic information to confirm if the beak changes are genetically driven and to rule out other factors like gene flow.
Experts not involved in the study, such as Ian Owens of Cornell University and Jeff Podos of the University of Massachusetts Amherst, noted the remarkable speed of these changes and the significance of long-term datasets in detecting such evolutionary pulses. The success of campus juncos in urban settings and their ability to adapt offer insights into how organisms might cope with human-induced environmental changes, providing a potentially hopeful message for wildlife conservation.