Some hummingbirds duel over females, fencing with their beaks STORRS, Conn., Nov. 4 (UPI) -- Next to their racecar-fast wings, perhaps the hummingbird's most noticeable feature is their long, narrow beak, which houses a lightening-quick tongue used to snatch nectar from flowers. It's long been assumed this hunt for nectar is the chief driver in the hummingbird's adaptation through natural selection, but new research suggests sexual competition also plays a role, as a variety of male hummingbirds use their beak as both nectar-sipper and sword -- dueling rivals for territorial advantage and sexual supremacy. The new study, carried out by scientists at the University of Connecticut, offers the first evidence of hummingbird bills being used as weapons. "Historically, bird beaks have been the prime example of adaptation through natural selection, such as in the textbook example of Darwin's finches," Alejandro Rico-Guevara, an evolutionary biologist and lead researcher on the study, said in a press release. "But we show here the first evidence that bills are also being shaped by sexual selection through male-male combat," Rico-Guevara added. It is exciting to think of all these forces working on the way animals look, and to think about how they might affect males and females differently. Scientists have previously noted gender differences in the shape and length of hummingbird bills, but had reasoned that such variation were the result of differing feeding patterns. Rico-Guevara focused his research on the long-billed hermit, a tropical hummingbird found in Costa Rica. He and his colleagues found male specimens grew longer sharper bills as they matured -- much longer and sharper than female bills, and capable of piercing a rival's throat. They also observed the males frequently using their bills during fights near prime mating locations. "I think people initially think of them as beautiful, delicate creatures," Rico-Guevara said, "but I enjoy revealing their pugnacious attitudes." The study was published this week in the journal Behavioral Ecology.