Wild crows can recognize individual human faces and hold a grudge for years against people who have treated them badly. Researchers at the University of Washington in Seattle and colleagues donned a rubber caveman mask and then captured and banded wild American crows. Whenever a person wearing the same mask approached those crows later, the birds scolded them loudly. In contrast, they ignored the same person wearing a mask of former US Vice-President Dick Cheney, which had never been worn during banding.
The birds’ aversion to the caveman mask has lasted more than three years, even though the crows have had no further bad experiences with people wearing it. The crows responded less strongly to other details of a person’s dress, such as the presence of a hat or a coloured armband.
Source: New Scientist