Crows can remember a human face for over 10 years and tell their friends which people are dangerous.

In 2006, Dr. John Marzluff and his team at the University of Washington tested crow memory. Researchers wore a caveman mask while trapping and banding seven crows. They also wore a different mask while doing nothing to the birds. The crows quickly learned to scream at anyone wearing the caveman mask while ignoring the other mask.The number of crows reacting to the mask grew over time. Even though only seven birds were trapped, more than 60% of the local crows eventually joined in the scolding. This behavior lasted for more than 9.5 years after the first encounter. Crows teach their children and their peers which faces represent a threat.In 2012, the team used brain scans to see how crows process these faces. When crows saw a dangerous face, the parts of their brain linked to fear and memory became active. This is very similar to how human brains handle emotional memories. Crows can pick out a specific face even when that person is standing in a large crowd.Crows have a large brain compared to their body size. This helps them survive in cities where they must tell the difference between people who feed them and people who hurt them. Their alarm calls are specific sounds that tell the rest of the flock how much danger they are in. This long-term memory is rare in birds and is more like the intelligence seen in dolphins or chimps.