City birds responded consistently to a test involving human gender, a finding that may inspire future studies about the relationship between urban wildlife and their human neighbors.
Birds fled sooner, and from farther away, when approached by women than when they were approached by men, according to a study conducted across five European countries and published in the journal People and Nature.
The Study
A total of 2,701 observations regarding 37 species of common birds that regularly frequent urban habitats were made during the spring breeding season of 2023 in Czechia, France, Germany, Poland, and Spain — all of which have rich avian biodiversity. Fieldwork was carried out mostly within the first four hours after sunrise, under calm, dry conditions, to limit outside sources of variation.
One male and one female participant, both professionally trained to conduct ornithological surveys, engaged in the test by walking at a leisurely, steady pace along a straight path toward the target bird until the moment it decided to take flight, recording the so-called flight initiation distance, or FID.
Both participants were matched for height and build, dressed comparably, and tied back their hair where applicable, so that clothing, height, and hairstyle would not explain any difference in the birds’ reactions.
After excluding species with fewer than ten recorded encounters, the researchers analyzed 2,581 observations across 37 species, among them frequently encountered urban species such as the Eurasian blackbird, common wood pigeon, Eurasian magpie, great tit, and house sparrow.
The results showed that birds reacted differently depending on the gender of the observer: on average, the mean flight initiation distance was about 8.5 meters for women and roughly 7.5 meters for men — meaning men were able to get about one meter, or roughly three feet, closer to birds before they took off, and birds gave women an estimated 11 percent more space overall.
The pattern was consistent both across the five surveyed countries and across bird species, holding for skittish species like magpies as well as bolder, more human-tolerant species like pigeons.
“This is maybe the most interesting part of our study,” said Federico Morelli, an associate professor at the University of Turin and 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.”
Yanina Benedetti, a researcher at the Czech University of Life Sciences Prague and a co-author of the study, commented on what the finding meant to her personally as a woman working in the field: “As a woman in the field, I was surprised that birds reacted to us differently,” she said, adding that the results show how animals see us in an urban context, and that this is worth understanding and considering.
Daniel Blumstein, a professor of ecology and evolutionary biology at the University of California, Los Angeles, and one of the study’s co-authors, said he stands behind the findings even though he cannot yet explain them.
He noted that the results suggest the gender of the person conducting an experiment could itself be a source of bias in studies of wildlife behavior — something researchers may want to control for going forward.
Explanation of Results
It remains unclear what accounts for the observed differences, though the researchers have proposed a handful of possible explanations, none of which has yet been tested individually.
The team has floated subtle differences in gait, posture, body shape, and scent or pheromones as candidate cues that birds might be detecting, even when clothing, height, and hairstyle are deliberately kept the same between observers.
Blumstein has gone so far as to half-jokingly suggest that properly isolating gait as a variable might require an experiment resembling the exaggerated walking styles of the British comedy sketch “The Ministry of Silly Walks,” a nod to how deliberately different two people’s movements would need to be to test the idea in isolation.
Benedetti has said the logical next step is to test these factors separately rather than grouping them together under observer gender.
Implications for Science, Society, and Everyday Life
The study’s implications touch several areas at once. First, the findings add to a growing body of evidence that animals respond differently depending on the gender of the humans they encounter.
It has previously been established that laboratory rats and mice show more signs of behavioral reactivity when handled by men than by women, and separate research on monkeys and pet dogs has found that these animals, too, can show preferences tied to a person’s gender. This study, however, marks the first time such a pattern has been documented and confirmed in wild birds living in cities.
Second, in terms of practical application, the study serves as a caution to field researchers investigating how wildlife responds to human disturbance. Because many behavioral studies assume that a human observer is a neutral presence, relying solely on observers of one gender risks missing part of the picture.
Third, for everyday life, the implications are mostly gentle ones. The study is not a claim that women are inherently more disruptive to urban wildlife, nor is it a reason to discourage women from spending time outdoors or working in the field. In practice, this mainly encourages people to be mindful of the subtle cues that city wildlife may be picking up on — and to move calmly and give animals a bit of extra space regardless of who is doing the approaching.
The study’s authors have also been careful not to overstate their findings. Although the pattern was strong and consistent across countries and species, the team has stressed that more research is needed to confirm how widespread the effect is and to identify what is actually driving it.
Ultimately, the study serves as a fascinating reminder that city animals are paying much closer attention to the people around them than most of us realize.
Sources
Morelli, F., Benedetti, Y., Mikula, P., Blumstein, D. T., et al. (2026)