Researchers who trapped crows while wearing a specific mask were scolded by the local flock for years afterward, even by birds that were never caught.

The crows appear to teach each other who is dangerous. Researchers who wore a neutral mask were left alone, which makes this one of the cleaner experiments in animal cognition.

Why it is in the vault: it is the kind of find worth coming back to. Add sources, corrections and related links in the discussion thread.