An elephant never forgets, but what about birds? Research suggests that angry crows can hold a grudge for years and can even communicate this feud to others.

Wearing special masks, researchers banded and released crows at several sites near Seattle. This ruffled a lot of feathers, leading to angry caws and dive bombing by released birds. Such scolding behavior attracted other crows to join the angry mob.

Later, when the birds saw people simply donning the masks, they mobbed the wearer from up to a mile away, even crows that had never been captured. So far, these brainy birds have remembered the insult for five years and counting.

Scientists suspect that this type of social learning may be common among long-lived species in close contact with people. So if you tick off a crow, coyote, pigeon or rat, don’t plan on getting a love letter anytime soon.