LA Birds Changed Beak Shape During COVID Lockdowns

Scientists watched evolution happen in real time when Los Angeles birds changed their beak shapes during the COVID-19 lockdowns, then changed back when people returned.

Researchers at UCLA tracked dark-eyed juncos, small gray sparrows living on campus, from 2018 to 2025. They discovered something remarkable: birds hatched during lockdown grew longer, slimmer beaks that looked just like their wild cousins, not the short, thick beaks typical of city birds.

City juncos normally develop chunky beaks perfect for chomping human food waste and handouts. But when lockdowns closed dining halls and cleared foot traffic, baby birds grew different beaks entirely.

The shift happened fast. Birds born during the quiet months developed beaks better suited for natural food sources in green spaces that people had abandoned.

Then, as human activity returned, so did the original beak shape. Later generations went right back to the shorter, thicker bills their urban parents once had.

"The most novel aspect of this study is the speed with which these changes are observed and, equally surprising, their reversibility when human activity is restored," said Inmaculada Álvarez-Manzaneda Salcedo, an ecology professor at the University of Granada who reviewed the findings.

The lockdowns created an accidental natural experiment. For the first time, researchers could isolate human presence as a specific pressure acting on city wildlife, like flipping a switch on and off.

Food availability likely drove the changes. Without dining facility waste, birds had to eat more natural foods, which required different beak tools.

The Bright Side

The findings reveal something hopeful about nature's resilience. Urban wildlife isn't locked into one path but can respond quickly when conditions shift.

The research team notes they're still investigating exactly how these changes happened so fast. It could be natural selection favoring certain existing traits, developmental flexibility, or a combination of factors.

What's clear is that city animals are more connected to our daily lives than we realized. When we briefly stepped back, nature stepped forward and adjusted within a single generation.

The discovery suggests urban spaces hold more potential for adaptation than scientists previously thought, opening new questions about how cities and wildlife can coexist and evolve together.