Research involving numerous European bird species—including great tits, house sparrows, and blackbirds—indicates that these birds can differentiate between male and female humans, responding accordingly. However, the underlying reasons for this behavior remain elusive.
Western Wagtail (Motacilla flava), small birds from the order Passeriformes and the family Motacilidae. Image credit: Sci.News.
“When facing potential predators, flight is the primary response across various animal species,” stated Daniel Blumstein, a professor at the University of California, Los Angeles.
“Evaluating the costs and benefits of escape is vital for managing predation risks.”
“Flight Initiation Distance (FID) is often utilized to explore the cost-benefit dynamics associated with these risks.”
“FID serves as a reliable measure of fear, reflected in the distance between the observer and the target animal when it decides to flee.”
“In urban birds, FID can effectively gauge predator-related apprehension, even in situations where humans approach without aggressive intent.”
In a recent study across five European nations (the Czech Republic, France, Germany, Poland, and Spain), participants—both male and female—walked directly towards birds located in urban parks and green spaces.
The study revealed that male observers could approach birds an average of 1 meter closer before the birds took flight compared to female observers.
These findings were consistent among the 37 bird species examined in all participating countries, ranging from fast-fleeing species like magpies to slower species like pigeons.
“Adjusting for other variables influencing FID, our research indicates that birds generally flee from a distance roughly 1 meter farther when approached by females compared to males,” the researchers stated.
“This suggests a lower tolerance among birds for female approaches, a trend observed consistently across diverse geographical locations.”
This leads to the conclusion that urban birds can perceive the gender of approaching humans.
However, the specific traits that prompt this detection and the reasons behind the heightened aversion to women remain unclear.
“We firmly stand by our findings that urban birds react distinctively to the gender of human observers, yet we currently lack a definitive explanation,” noted Professor Blumstein.
“Utilizing advanced comparative analysis techniques, we confirmed consistent results across various cities and species, leaving us puzzled regarding the underlying factors.”
Dr. Janina Benedetti from the Czech University of Life Sciences in Prague remarked, “As a female researcher in the field, it was surprising to see differing reactions from the birds.”
“This study sheds light on how urban wildlife perceives humans, which holds significant implications for urban ecology and the representation of diversity in scientific research.”
“Many behavioral studies presume human observers are neutral; our study illustrates this assumption doesn’t hold true for urban birds.”
The research team has proposed several hypotheses regarding potential factors, such as pheromones, body shape, and gait.
“This aspect of our study is particularly intriguing,” commented Dr. Federico Morelli, a researcher at the University of Turin.
“We’ve identified an interesting phenomenon, yet the reasons remain unclear.”
“Our findings highlight the birds’ advanced capabilities in environmental assessment.”
“Urban birds evidently react to subtle cues that often go unnoticed by humans,” concluded Benedetti.
Future studies could focus on individual aspects such as behavior patterns, olfactory signals, and physical traits, allowing for a more targeted investigation into the specific cues that birds may recognize.
For further information, refer to the findings published in the February 2026 issue of the journal People and Nature.
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Federico Morelli et al. 2026. Sex matters: European urban birds flee faster when approached by females than when approached by males. People and Nature 8 (2): 316-326; doi: 10.1002/pan3.70226
Source: www.sci.news
