- John Marzluff went undercover to test the birds' reactions to being caught and tagged.

- When we first captured birds, we were wearing this mask, so the birds that were immobile under a net saw this person coming to them, grabbing them, stretching their wings out to measure them, applying rings to their legs to identify them, and then letting them go.

- Crows don't like being caught, even when they're unharmed, so the question was: would they remember that the masked man was a threat?

A few days after the initial tagging, Marzluff walked across the campus again.

He kept the mask on, but he left the crows alone to see if he'd get any response.

- It was very striking.

The first time after we did this experiment and we walked with the caveman mask, birds immediately responded to that.

They scolded with harsh calls that are indicative of a predator, and they gathered around us.

They attracted others in and they would even dive down at us.

- Marzluff discovered that the crows were somehow telling each other that the person in the caveman mask was dangerous.

And what's more amazing, even though the team never again caught crows with the mask on, that reaction has been passed down through several generations.

- It's been 11 years since we caught seven birds on our campus with this mask, and nearly half of all the birds we encounter on a given day respond strongly to that face, even though they weren't even born at the time we first did our capture, the only experience they have with that caveman is hearsay.