Francois Gohier/ardea.com

Crows belong to a group of birds called corvids, known for their intelligence. They are loyal birds, forming long-lasting social relationships with specific individuals.

To find out how they form new relationships, Miriam Sima at the Max Planck Institute for Ornithology in Germany, and her coauthors studied crows that were unfamiliar to each other. They wanted to see how the crows would react to scuffles amongst relative strangers.

The team kept carrion crows, native to Europe and Asia, in a cage. When they put food into the cage, they noticed the birds fought more when the food …