(Image source: LiveScience)

BY: STEVEN SPARKMAN

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Crows are smart, they carry grudges, and they’re organized. A new study shows not only do crows remember humans who’ve threatened them, they teach other birds to carry on the vandetta.  The saga began five years ago with a University of Washington researcher. New Scientist explains.

“He briefly trapped American crows on his university's campus while wearing a distinctive ‘caveman’ mask. Afterwards, crows that had been trapped scolded anyone they spotted wearing the caveman mask, following them around and cawing harshly...”

Scolding can quickly turn into mobbing, where many crows follow a target around, cawing and dive bombing them. In early June, the town of Everett, Washington, saw this behavior firsthand when the crows apparently decided they didn’t like police officers. (Video source: WPVI)

But researchers noticed this mobbing behavior increased over time. They wondered whether crows just can’t resist a good mobbing, or whether they were actually teaching each other who to scold. LiveScience reports how they got their answer.

“To find out, the researchers tested a ‘dangerous’ mask and a neutral mask on fledgling crows while their parents were in the nest and also while their parents were away. They found that the presence of a grudge-holding leader wasn't necessary: If the baby birds had ever seen their parents scold the mask, they started scolding it even when mom and dad weren't around.”

So not only do crows recognize individual threats, they also teach other crows who the bad guy is. Five years later, the caveman mask gets scolded more than ever -- even when the birds go a year without seeing it. A writer for io9 suggests not giving the birds a reason to scold you.

“Researchers have only tested crow memory for five years, but they believe that the birds remember faces for their entire lives -- fifteen to forty years. Get on the wrong side of one crow in your forties or fifties, and you could be mobbed everywhere for the rest of your life.”

If you do get on the crows’ list, you could do what Everett officials recommended for their scolded cops: carry an umbrella.

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Transcript by Newsy.