Crows Can Remember Human Faces for Years

Crows can recognize individual human faces, remember people who stress them for years, and pass warnings about them to other crows.

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Crows are unusually good at recognizing individual people. Research on wild American crows found that birds could learn to identify a particular human face after a stressful encounter and continue reacting to that face years later. In controlled field studies, crows were exposed to people wearing distinctive masks while the birds were captured and handled. Later, the birds were much more likely to scold and mob the person wearing the mask linked to that experience than people wearing neutral masks. One study found that this recognition lasted at least 2.7 years. The behavior can also spread socially. Crows that were not captured could learn about a threatening person by observing other crows, and young birds could acquire the response from their parents. This means a crow does not necessarily need to experience a threat firsthand to learn that a particular human should be avoided. Brain research has also found that several connected regions in the crow brain become active when the birds process human faces associated with different experiences. The popular idea that crows hold grudges is therefore rooted in a real ability to remember individual humans and associate them with past events, although the scientific evidence is more precise than the everyday word grudge suggests.

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