The real story
At the University of Washington in Seattle, wildlife biologist John Marzluff and his team wore a rubber caveman mask while trapping and banding seven crows on campus. Afterwards, anyone walking through campus in that mask got mobbed and scolded, even when it was worn upside down or under a hat. People wearing a neutral control mask were mostly ignored.
Over the following years the scolding spread to crows that had never been trapped, including birds hatched after the experiment, which learned it from their parents and neighbours. Later brain-scan work showed crows process threatening faces in regions linked to fear and learning. The grudge lasted about 17 years: on a masked walk in September 2023, no crow scolded at all.
