Hummingbirds live across North and South America. The tiny birds have long, slender beaks to sip sweet nectar from flowers. But a new study has found that some of the birds’ beaks also have another purpose: battle.

Researchers took photos and videos of male hummingbirds fighting in Colombia, Brazil, Peru, and Costa Rica. Then they analyzed the beaks of these birds in the lab. Unlike most hummingbirds, the battling birds tended to have beaks with jagged teeth and hooked tips. 

These adaptations help the hummingbirds duel over mates and protect flower patches where they feed. “We’ve recorded these males using their beaks as weapons to fight,” says lead author Alejandro Rico-Guevara.