Hummingbirds are usually seen as fragile, harmless little birds that flutter around between flowers innocently sipping nectar. But there are some hummingbirds that live secret lives ... as master swordsmen.

Deep in the jungles of South America, competition between hummingbirds can be fierce, with as many as 15 different species swashbuckling over the same resources. Many of these species have had to evolve specialized beaks that do far more than suck nectar; they must also fend off competitors, both for food and for mates.

When you look close enough, the sleek beaks of these birds start to look more like swords or knives than feeding apparatuses. Some are lined with tooth-like serrations, while others end in sharp points.

Now for the first time, researchers have captured these incredible fencing hummingbirds in action by using high speed cameras, reports Phys.org.

"We understand hummingbirds' lives as being all about drinking efficiently from flowers, but then suddenly we see these weird morphologies — stiff bills, hooks and serrations like teeth — that don't make any sense in terms of nectar collection efficiency," said Alejandro Rico-Guevara, lead scientist on the project. "Looking at these bizarre bill tips, you would never expect that they're from a hummingbird or that they would be useful to squeeze the tongue."

The results of the study might change your perception of these birds forever. It turns out, hummingbirds can be vicious and skilled fighters. Researchers report observing impressive fencing skills, which involves mid-air stabbing, slashing, and plucking of feathers.

The cost of being feistier

Males are usually the ones with the most specialized fighting-beaks, indicating that they are probably fencing more to compete for mates than for food resources.

"We are making connections between how feisty they are, the beak morphology behind that and what that implies for their competitiveness," explained Rico-Guevara.

Interestingly, different species of these sword-beaked hummingbirds appear to be walking a fine evolutionary line between feeding proficiency and swordplay. The more specialized the beaks are for fighting, the more difficult it can be to collect nectar from flowers. The serrations, point-tips, and hooks of some beaks really get in the way of navigating delicate flowers.

So, fencing hummers must utilize different strategies for securing food resources to make up for their lack of efficiency.

"We have discovered that these traits may be related to a different kind of strategy: instead of feeding on a particular flower shape very well, some birds try to exclude everybody from a patch of flowers, even though they can't feed as well on them as hummingbirds without bill weapons," explained Rico-Guevara. "If you are good enough at keeping your competitors away, then it doesn't matter how well you use the resources in the flowers you are defending, you have them all to yourself."

The next step for researchers will be to further analyze the trade-offs between fighting and feeding among these birds, to better understand their behavior and unravel the mysteries of their evolution. It's certainly a new way of looking at these charismatic avians.

The secret lives of hummingbirds with sword-like beaks
Some hummingbirds have evolved beaks better suited for fencing than feeding.