Wrong a crow once and it never forgets. In a 2011 University of Washington study, researchers wearing a rubber caveman mask trapped and banded wild American crows — then walked the same campus for years afterwards. The crows scolded and mobbed the mask every single time, more than five years later. Crows that were never trapped did it too: the birds had learned the dangerous face from their flock and passed it to their offspring.

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If you've ever messed with a crow, it will remember your face — possibly for the rest of its life. In 2011, scientists at the University of Washington ran an experiment where they trapped wild crows while wearing a specific rubber caveman mask. They then walked the same campus wearing that mask again — and the crows went berserk. They scolded, dive-bombed, and recruited other crows that had never even seen the mask to join the mobbing. The memory held for at least five years. Even more striking — crows that were chicks during the original trapping grew up, learned the dangerous face from their parents, and mobbed it too. That means crows are passing grudges down through generations. So next time you shoo one away, think twice. Follow for a fact every day.