Presumably, hummingbird beaks evolved to reach the nectar at the bottom of flowers, but that’s not all: Male hummingbirds also use them a stabby murder-spears in fights over females, according to a new study.

“Historically, bird beaks have been the prime example of adaptation through natural selection, such as in the textbook example of Darwin’s finches,” says Alejandro Rico-Guevara from the University of Connecticut. “But we show here the first evidence that bills are also being shaped by sexual selection through male-male combat.”

The study, which focused on a Costa Rican species known as the long-billed hermit, observed the males fighting in what’s known as a lek. When a female is present and begins singing her mating songs, the males begin to fight with one another to secure territory for mating. This is believed to be the first known instance of male bird bills evolving to be used as weapons.

Though differences in male and female bird beaks were previously attributed to disparities in feeding habits, that may not be the only factor. Rico-Guevara and co-author Marcelo Araya-Salas from New Mexico State University found that male hummingbirds developed beaks that were not only longer, but sharper, at puberty.

Not surprisingly, males with the longest, sharpest beaks tended to be most successful in defending territories, using them to stab at the necks of opponents. It boils down to the advantage of bringing a longer lance to a jousting match, or a broadsword to a knife fight.

Now, researchers have a lot of questions about evolution in general. Is it possible that the beaks evolved entirely separate from flowers, and that flowers actually evolved to accommodate the shape of the birds’ beaks?

“I think people initially think of them as beautiful, delicate creatures,” says Rico-Geuvara, “but I enjoy revealing their pugnacious attitudes.”