In European parks, birds take flight about 1 meter sooner when approached by a woman than when approached by a man. The finding rests on 2,701 trials conducted in France, Spain, Germany, Poland, and the Czech Republic. Neither height nor clothing explains the difference, as the researchers had deliberately controlled for these two factors.
Why this gap exists remains unknown.
- Birds take flight roughly 1 meter earlier in front of a woman than in front of a man.
- The gap was observed across 2,701 trials in five European countries.
- Height and clothing had been controlled for, and the cause remains unknown.
Two walkers, same height, same outfit
The protocol rests on a simple idea. Pairs consisting of a man and a woman of equal height, dressed identically, walked in a straight line toward birds in parks and urban green spaces. Each trial ended the moment the bird fled. This precaution rules out the most obvious explanations, such as a larger frame or a jacket of another color.
What researchers recorded is called the flight initiation distance, the gap between the human and the bird at takeoff. Ecologists have used this measure for a long time to gauge risk perception: the longer the distance, the more risk-averse the animal is. A bird that leaves early is a cautious bird.
The team, international in scope, is coordinated by Federico Morelli of the University of Turin, and among its signatories is Daniel Blumstein of UCLA. According to the authors, no study had yet tested the effect of the observer’s sex on the escape of wild birds. The work appeared in the journal People and Nature, published by the British Ecological Society, which highlighted it in October 2026 in a press release.
One metre, 37 species, five countries
One meter may seem trivial, until you consider how it was obtained.
The 2,701 trials cover 37 species: tits, sparrows, blackbirds, magpies, pigeons. Some flee very early, like magpies; others hold firm until the last moment, like pigeons. The gap nonetheless shows up across all of them, and in each of the five countries. When two people of the same height, dressed identically, produce the same offset for birds that are so different, chance becomes a difficult explanation to defend.
In terms of a pedestrian’s pace, a meter is roughly a long step. It’s the gap between the pigeon still pecking in front of you and the one that has already taken off. The effect remains an average calculated from thousands of trials: on a park bench, no observer would notice it at a glance, and that is probably why it had escaped scientists.
This regularity lends weight to the result, to the point that its authors themselves were surprised. Federico Morelli acknowledged that the team did not expect to see birds depart earlier in front of women. The researchers were mainly aiming to study the tolerance of urban birds to human presence, not to draw a sex-based comparison.
What the researchers do not know yet
“I fully believe in our results, but I do not know how to explain them yet,” summarizes Daniel Blumstein. A researcher who defends his data while admitting ignorance is rather unusual in a press release.
Several avenues are circulating. Birds might respond to chemical signals such as pheromones, to differences in morphology, or to the way men and women walk. These hypotheses remain speculative: the press release notes that additional experiments will be necessary to identify the actual cause. Future protocols will therefore need to isolate these parameters one by one—movement, odor, silhouette—something the current setup could not disentangle.
The study measures a flight distance, not a judgment. It does not state what the birds perceive, nor which cues they rely on, and it offers no behavioral explanation on the human side. The wording in some outlets that talk of birds “more frightened by women” condenses an average into an emotion that the scientific article itself does not measure.
Another finding appears in the article’s abstract: male birds appear more tolerant of risk than females. The authors conclude that further research is needed to fully understand the phenomenon.
Source: besjournals.onlinelibrary.wiley.com
