Birds in cities fly away faster when women approach than when men do, a new study found.
Researchers matched men and women for height and clothing, then sent them to approach birds in European cities. They found that men were able to get about a metre closer than the women before the birds flew away.
“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,” study author Daniel Blumstein told the British Ecological Society.
The study had consistent findings across 37 bird species and five European countries.
The sex of the bird studied, amount of tree cover, and the distance from which the human approached all had an effect on when the birds took flight.
- READ MORE: Bird Brain: New study finds birdwatching may boost brain health and slow cognitive aging
- READ MORE: Wild parrots copy their friends when deciding whether to try new foods, study finds
“Differences in the physical appearance of observers (e.g. hair length, body size, height, etc.), movement patterns (e.g. hip movement, overall walking gait) or different clothing could be candidate factors. But we can reject these because, in our study, they were either controlled or their differences were non-significant,” the study found.
“We can reject gross morphology, since the woman and man working at a given site were similarly tall and hid their hair if it was longer than their partner’s.”
The study authors warned that birds may be able to detect differences in hair length, style, waist-hip ratio, gait, odour, or other differences in humans.
CTV News’ science and technology specialist Dan Riskin, who was not involved with the study, said the findings were remarkably consistent but there is room for future study.
“Most wild animals are scared of humans,” Riskin said, adding that “humans eat almost everything.”
“Most animals that have spent any time with humans through evolutionary time run away from them.”
Riskin added that birds may perceive things in humans that humans don’t notice in themselves and therefore can’t control for in a study. He suggested humanoid robots as a potential next research step, to try and isolate what exact mannerisms triggered birds to fly away.
The researchers also say that based on their results “we can speculate that women, if they hunted, could have focused more on smaller prey (e.g. birds), while males hunted mainly larger prey.”
Riskin agreed, saying there is likely an “evolutionary story” behind the study findings.
“Men were probably hunting bigger game and women were probably doing more of the foraging close to home where there were kids,” he said. “We believe that if they were hunting, it was probably for smaller animals than what men were hunting.
“We don’t know that for sure, that’s a lot of assumptions, but it might help explain why a bird might be more wary of a female human approaching compared to a male human approaching.”
- READ MORE: Birds with bigger brains may cope with climate crisis better, study suggests
- READ MORE: Why birds sang after a total solar eclipse, according to new research
The study found that birds generally prefer to retreat to trees, rather than bushes or human-made structures, when approached. They also report birds fleeing earlier when humans approached from farther distances.
“The observed pattern may stem from birds considering longer approaches as more purposeful, and thus, a higher predation risk,” the authors wrote.
Researchers emphasized that their findings were only preliminary and required further research.
“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,” co-author Federico Morelli told the British Ecological Society.
“Urban birds clearly react to subtle cues that humans do not easily notice,” co-author Yanina Benedetti added, “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.”
