Birds fear women more than men, and scientists don’t know why

An international team of researchers have made the surprising discovery that urban birds - such as great tits, house sparrows and blackbirds - flee sooner when approached by women compared to men. But they don’t understand why.

Conducted across five European countries, the study involved male and female participants (matched for height and clothing) walking in a straight line towards birds in urban parks and green spaces.

The researchers found that compared to women, men were able to get an average of one metre closer to birds before they fled (termed flight initiation distance). The results, published in the British Ecological Society journal, People and Nature, were consistent across all five countries: Czechia, France, Germany, Poland and Spain.

This finding was also consistent across the 37 bird species studied, from species that typically flee early, like magpies, to species that flee late, like pigeons.

From the results, the researchers conclude that urban birds can recognize the sex of the humans approaching them. But what traits the birds are picking up on or why they are more fearful of women remain a mystery.

Professor Daniel Blumstein from the University of California, Los Angeles, a co-author of the study said: “I fully believe our results, that urban birds react differently based on the sex of the person approaching them, but I can’t explain them right now. We used bleeding-edge comparative analysis techniques that showed our findings were consistent across cities and species, but we simply don’t have a conclusive explanation yet.”

Dr Yanina Benedetti from the Czech University of Life Sciences Prague, another co-author of the study added: "As a woman in the field, I was surprised that birds reacted to us differently. This study highlights how animals in cities ‘see’ humans, which has implications for urban ecology and equality in science. Many behavioural studies assume that a human observer is neutral, but this wasn’t the case for urban birds in our study.”

The researchers have a few hypotheses for what birds are detecting, such as pheromones, body shape or gait, but say these are speculative and that more research is needed.

“This is maybe the most interesting part of our study” said Dr Federico Morelli from the University of Turin, a co-author of the study. “We have identified a phenomenon, but we really don’t know why. However, what our results do highlight is the birds’ sophisticated ability to evaluate their environment.”

Dr Benedetti said: “Urban birds clearly react to subtle cues that humans do not easily notice. Follow up studies could focus on individual factors such as movement patterns, scent cues, or physical traits, testing them separately rather than grouping them under observer sex. This approach would help identify the specific cues birds detect.”

While the study contained 2701 observations, the researchers caution that these still represent preliminary findings and that more research is needed to confirm the consistency of the observed sex-related pattern.