- Crows remember the faces of "dangerous humans," with the memories likely lasting for a bird's lifetime.
- Crows may scold people who threaten them, bringing in relatives and even strangers to mob the person.
- The crows within mobs then indirectly learn about the person, so they too associate that individual's face with danger and react accordingly.
Crows remember the faces of threatening humans and often react by scolding and bringing in others to mob the perceived miscreant, according to a new study published in the latest Proceedings of the Royal Society B.
Since the mob members also then indirectly learn about the threatening person, the findings demonstrate how just a single crow's bad experience with a particular human can spread information about this individual throughout entire crow communities.
Given that crows have impressive memories, people who ruffle the feathers of these birds could experience years of retribution.
Bothered crows may at first "give harsh calls, which we call 'scolds' that attract other crows who are nearby to join in the mob," according to study co-author John Marzluff. "The mob of two to 15 birds hounds us, sometimes diving from the sky to within a few meters or less -- This pursuit lasts about 100 meters (328 feet) as we walk away."
Marzluff is a professor at the University of Washington's School of Forest Resources. For the study, he and colleagues Heather Cornell and Shannon Pecoraro exposed wild crows to a novel "dangerous face" by wearing a unique mask as they trapped, banded and released seven to 15 birds at five study sites near Seattle.
The released birds immediately scolded the mask wearer. Hearing the racket, other crows joined, forming an angry mob.
When the researchers later put on other masks while traveling to different areas, crows that were never captured immediately recognized the "dangerous face," illustrating how these birds learned through social means and not as a result of direct experience. Both relatives and strangers joined in the scolding and mobbing, which could occur over a mile away from the original incident.
Once such a face is locked into a crow's memory, it's likely there for good.