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Nº 092 · Nature · 45 sec

Crows remember who harms them – and pass it on

Researchers caught crows while wearing a mask. Years later, crows that had never been caught were scolding it too.

Head of a black crow with a strong beak, close-up against a light background
Photo: cuatrok77 · CC BY 2.0 · Original

The experiment

A team from crow researcher John Marzluff's lab at the University of Washington caught wild American crows near Seattle, banded them and let them go. While doing so, the researchers wore a distinctive mask, the "dangerous face". At five sites they caught 7 to 15 birds each.

Your guess

Who scolded later when someone wearing the mask showed up?

How the warning spreads

1.2kmat least this far the scolding spread at one site within five years

At one site the scolding doubled within five years and reached at least 1.2 kilometres away. So knowledge about a dangerous person travels from crow to crow – even to crows that never had a bad experience themselves.

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