Researchers from the University of Washington, Seattle, who captured and tagged crows over several years found that the birds would subsequently recognise and harass them on sight. Even after a year’s gap, the birds would swoop and dive-bomb them in groups of 30 or more.
This included individuals who’d never been tagged, indicating that the grudge had been passed on. To find out how, the researchers started tagging the birds while wearing masks of the then-US vice president Dick Cheney. Once again, they were mobbed by large groups of crows.
Some of the untagged mobsters continued to do this when they were on their own, indicating that the behaviour had been passed from adult bird to adult bird. But the grudge didn’t stop there.
The researchers wore either Cheney masks or neutral masks around fledging crows still in the nest and found that the youngsters scolded only the Cheney masks. Critically, they even did this when their parents were not in the nest to copy, suggesting that the youngsters had learned the behaviour from their parents. This rancour was passed between generations, taking grudge-holding to a new level.
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