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Black-headed Gulls in Kunming Fled at Similar Distances From Women and Men

Black-headed gull in winter plumage flying
Research · Behaviour

Wintering black-headed gulls (Chroicocephalus ridibundus) in tourist areas of Kunming, China, began to move away at similar distances whether the approaching observer was a woman or a man. The study, published on 12 August 2026, found no statistically significant overall effect of observer sex on the birds’ flight-initiation distance.

Flight-initiation distance is the distance between an approaching potential threat and an animal when the animal begins to escape. It is widely used to study how birds balance the risk of remaining in place against the costs of leaving. The fieldwork used 23 female and 22 male observers at four tourist sites in Kunming. They approached free-living, wintering black-headed gulls and compared flight-initiation distances between the two observer groups.

Individual observers differed substantially from one another

The study was motivated partly by earlier work in five European countries, where urban birds had fled sooner from approaching women than from men. The Kunming gulls did not show the same broad pattern. Escape distances varied widely within both observer groups, and the analysis detected significant differences among individual observers.

The individual variation shows that observer sex alone did not account for the differences among people approaching the gulls. The authors suggest that subtle differences in behaviour or appearance among individual people may have influenced the birds more strongly than observer sex. They also propose that long exposure to large numbers of tourists with diverse behaviour may have made sex-related cues less informative for these gulls.

Both explanations remain interpretations rather than mechanisms demonstrated by the experiment. The result shows that observer sex did not produce a consistent difference in flight-initiation distance under the Kunming study conditions; it does not show that black-headed gulls cannot distinguish women from men in other contexts.

Sources and image credit

  1. Are black-headed gulls less tolerant of women than of men?Peer-reviewed field study comparing flight-initiation distances under approaches by female and male observers at four Kunming tourist sites.
  2. Dataset: Are black-headed gulls less tolerant of women than of men?Primary dataset and documentation associated with the study.

Image: Black-headed gull (Chroicocephalus ridibundus) in winter plumage in flight, photographed in France on 26 October 2025. Photo: Alexis Lours. Source: Wikimedia Commons. CC BY 4.0. Representative image; not a bird from the Kunming study. · CC BY 4.0 · Source

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