The surprising behavior suggests that birds may be able to distinguish between male and female humans. It also raises new questions about how urban wildlife perceives the people sharing its environment.

Urban birds kept a greater distance from women

The study was conducted in five European countries. Male and female participants, matched for height and clothing, walked directly toward birds in city parks and other green spaces.

On average, male participants were able to get about a meter closer to the birds before they flew away. Researchers measured this response using flight initiation distance—the distance between a person and a bird when the bird takes off.

Published in the British Ecological Society journal People and Nature, the study found the same pattern in the Czech Republic, France, Germany, Poland and Spain. The difference appeared across all 37 bird species examined, including magpies and pigeons, which are generally more accustomed to people and easier to approach.

Why are birds more wary of women?

Researchers believe the findings show that urban birds can distinguish between male and female humans. However, they do not yet know which traits birds recognize or why birds appear to be more cautious around women.

Daniel Blumstein, a professor at the University of California, Los Angeles, who helped conduct the study, said the results were convincing despite the lack of a clear explanation.

“While we fully believe in our results that urban birds respond differently depending on the gender of an approaching person, we currently cannot explain it. We used state-of-the-art comparative analysis techniques to show that our findings are consistent across cities and species, but we still do not have a definitive explanation.”

Dr. Janina Benedetti of the Czech University of Life Sciences in Prague said the findings challenged her expectations about how birds would respond to human observers.

“As a woman in the field, I was surprised to see how birds reacted differently to us. This study highlights how urban animals ‘see’ humans, which has implications for urban ecology and equity in science. Many behavioral studies assume that human observers are neutral, but this was not the case for urban birds in our study.”

What do birds sense in humans?

Scientists have proposed several possible explanations for the difference. Birds may respond to chemical signals such as pheromones, variations in body shape or differences in the way men and women walk.

For now, however, these explanations remain speculative. Additional experiments will be needed to determine which specific cues influence the birds’ behavior.

Study co-author Dr. Federico Morelli of the University of Turin said the unanswered questions were among the most fascinating aspects of the discovery.

“This is probably the most interesting part of our study,” Morelli said. “We’ve identified a phenomenon, but we don’t really know why. But what our results highlight is the sophisticated ability of birds to assess their environment.”

The findings suggest that urban birds may be sensitive to human traits that people themselves rarely notice. Identifying those signals could help researchers better understand how wildlife assesses potential threats in environments shared with humans.

Dr. Benedetti said:

“Urban birds clearly respond to subtle cues that are difficult for humans to notice. Follow-up studies could focus on individual factors such as behavioral patterns, odor cues, and physical characteristics, examining them individually rather than grouping by observer gender. This approach could help pinpoint the specific cues that birds pick up on.”

More research is needed to explain bird behavior

The study included 2,701 observations, but the researchers emphasized that the results are preliminary. Further research is needed to determine whether differences in bird responses to men and women appear consistently in other environments and bird populations.

For now, the findings offer an intriguing possibility: birds living in cities may be paying attention to subtle differences between humans that scientists do not yet fully understand.