A ScienceDaily report, based on material from the British Ecological Society, describes a study in which urban birds took flight sooner when approached by women than by men. The pattern appeared across five European countries and 37 bird species, but the researchers say they do not yet know what birds were responding to.
The study took place in Czechia, France, Germany, Poland and Spain. Male and female participants, matched for height and clothing, walked directly toward birds in city parks and other green spaces. Researchers recorded the flight initiation distance: how close a person could get before a bird took off.
Across 2,701 observations, men were able to approach about one metre closer on average before the birds flew. The report says the difference appeared in all 37 species studied. They included great tits, house sparrows and blackbirds, as well as magpies and pigeons, which typically let people come closer.
The researchers interpret the pattern as evidence that city birds may distinguish between male and female humans. The observations do not establish which cues birds notice. Chemical signals, body shape and differences in walking style are among the possibilities discussed in the report, but each remains speculative.
That uncertainty is part of the result. Professor Daniel Blumstein of the University of California, Los Angeles, who helped conduct the research, said in the report that he found the results convincing but could not explain them. Dr. Yanina Benedetti of the Czech University of Life Sciences Prague said the finding surprised her and challenged the assumption that a human observer is neutral in behavioral studies. Dr. Federico Morelli of the University of Turin, identified as a co-author, likewise described the cause as unresolved.
The findings matter for urban ecology because researchers often observe animals in places shared with people. If birds respond differently to characteristics of the person approaching, observer effects could shape measurements of how close wildlife allows a person to get. The report therefore raises a practical research question: whether studies should account for who is observing, as well as where and how observations are made.
The report emphasizes that the investigation is preliminary. Its results cover many species and several countries, but the researchers say further work is needed to establish whether the difference also occurs in other settings and populations. Follow-up studies could test movement, scent or physical traits separately, rather than treating observer sex as a single explanation. Until those cues are tested, the study identifies a consistent pattern in the sampled birds without explaining its cause.
<a href="https://www.sciencedaily.com/releases/2026/10/261021231250.htm">Source: ScienceDaily report</a>