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Hummingbirds are unique in many ways. Some of the the smallest birdsÌýin the world,Ìýthey are theÌýfastest fliers relative to their body length, andÌýthey are also the only true hoverers in the avian class. To enable this special form of flight, hummingbirdsÌýhave evolved several distinct adaptations, fromÌýa specializedÌýwing shape toÌýbreast muscles that take up about 30 percent of their entire body weight (most birds’ breasts weigh in at around 15-18 percent).

Scientists have always suspected that thisÌýcomplex movementÌýrequires a more complex brain, butÌýhummingbirdÌýbrains areÌývery smallÌýandÌýhard to study. So much soÌýthatÌýonly recently didÌýa team of Canadian scientists Ìýhow hummingbird brains handle hovering. Their research,Ìýpublished in this month’s edition of Current Biology, shows that hummers have brains unlike any other bird (or four-limbed vertebrate, for that matter), which letÌýthem manage multidirectional flight.

To understand these differences, it's first important to considerÌýhow and why we move. Every creature on Earth is either predator or prey, and many are both depending on where they fall in the food chain.ÌýFor almost all animals, this meansÌýmoving forward—i.e.,Ìýwhichever way they are facing—either towardÌýfood or away from becoming food. Humans are a rare exception among vertebrates in that we have the capability to move relatively efficiently in many directions. (Have you ever seen a dog try to trot backwards or climb a ladder?)

Despite this difference, our first instinct when faced with dangerÌýis still to turn around and run away from the threat,Ìýnot waltz sideways to safety. This instinct can be traced to the way our brains perceive motion.ÌýThe visual centers in the brainsÌýof all studied four-limbed creatures respond most strongly to motion on the back-to-front axis (think of us chasing somethingÌýor something chasing us).

Except for hummingbirds, according to the new research. Hummingbirds spend a lot of their time hovering, which means they have more to consider than just the frontÌýback-to-front axis. ÌýWhen hovering, a gust of wind might push themÌýfrom the side. Or aÌýpredator might strike from below. So theyÌýhave to be able to move not just in the forward direction to feed on a danglng flower, but in all directions.

Because of this, itÌýwould make sense that hummingbirds' brains don't put the same emphasis onÌýback-to-front movement thatÌýours do—and that’s exactly what the scientists found. The research team discovered that in an area of the brain called the lentiformis mesencephali, which is the part that responds to visual stimuli, hummingbirds didn’t have a strong back-to-front preference like all other animalsÌýtested thus far. Instead, they seemed to have no preference, responding to motion in every direction equally.

The researchers also found that hummingbirdÌýbrains are tuned to respond more strongly to fast movements than slow ones. This was a surprise because scientists had assumed that their brains would be tuned for a low-speed hover. ButÌýif you think about it, being optimized for high speed makes sense, too. AnÌýÌýcan moveÌýat 385 body lengths per second during mating flights, which is (in comparison,Ìýan F15 Eagle fighter jet has a top speed of Mach 2.5, which translates to around 45 body lengths per second). At that speed, the ability to make near-instantaneous course corrections is the difference between life and death—or mating and not mating, whichÌýis basically the same thing in evolutionary terms.

That hummingbird brains perceive the world differently than other vertebrates is a fascinating ornithological find,Ìýbut the researchers have other motivations for their study—understanding flight in natureÌýto design better robots. The discovery of an animal brain that can move efficiently in three dimensions could be very valuable for artificial intelligence inÌýflying drones, for instance, or computerized autopilot systems for helicopters. But potential commercial applications aside, isn’t it interesting to think that the tiniest bird brains might also be the most complicated?