Hummingbirds may be harbingers of spring and summer, but they don't have much time to stop and smell the roses. They have no sense of smell, for one thing, and they're also too busy gobbling up nectar to fuel their breakneck metabolism, which is the fastest of any warm-blooded animal on the planet.
All this energy enables some amazing physical feats. Hummingbirds flap their wings about 80 times a second, breathe 250 times a minute and experience more than 72,000 heartbeats every hour. Some also endure epic migrations, like the 500-mile nonstop flights of ruby-throated hummingbirds across the Gulf of Mexico or the 3,000-mile adventures of rufous hummingbirds between Alaska and Mexico.
Because they're always just hours from starvation, hummingbirds can't afford to stop feeding every time it storms, nor can they afford aerial blunders as they buzz around in search of food. And so they don't — hummingbirds keep foraging even in strong wind and rain, and they rarely stumble or crash. To shed light on how the birds maintain their aerial acrobatics, both in calm and blustery conditions, biologists have begun taking a closer look at what makes hummingbirds such expert aviators.
In one new study, researchers from the University of British Columbia investigated how hummingbirds fly so precisely under normal conditions. They placed the birds in a 5.5-meter (18-foot) tunnel, equipped with eight cameras to track their movement, then projected patterns on the walls to see how they steer to avoid collisions.
"Birds fly faster than insects, and it's more dangerous if they collide with things," lead author and UBC zoologist Roslyn Dakin says in a statement. "We wanted to know how they avoid collisions and we found that hummingbirds use their environment differently than insects to steer a precise course."
Bees judge distance by seeing how quickly an object moves past their field of vision, the study's authors note, since nearby objects pass by more quickly than objects located farther away on the horizon. When the researchers simulated this effect on the tunnel walls, however, the hummingbirds didn't react. Instead, the birds seemed to rely on the size of an object to assess its distance — a strategy that might help explain why they crash less often than bees do.
"When objects grow in size, it can indicate how much time there is until they collide even without knowing the actual size of the object," Dakin says. "Perhaps this strategy allows birds to more precisely avoid collisions over the very wide range of flight speeds they use." On top of that, the researchers also found that hummingbirds use a technique known as "image velocity" to determine altitude, adjusting their flight based on vertical movement of patterns on the tunnel walls.
Here's a video showing the results of their research:
In another recent experiment, biologists sought to learn how hummingbirds fly so well in wind and rain. To do that, they filmed the birds with high-speed cameras at the University of California-Berkeley's Animal Flight Laboratory.
The researchers used Anna's hummingbirds, a common species along North America's Pacific Coast. Once the birds learned to feed from an artificial flower, they were moved to a wind tunnel and hit with wind ranging from 7 to 20 miles per hour. Their reactions were recorded with a high-speed camera at 1,000 frames per second, followed by another experiment in which they tried to feed during a fake rainstorm inside a Plexiglas cube. Check out the video below, courtesy of KQED San Francisco:
While most birds flap their wings up and down, hummingbirds hover near flowers by rapidly flapping back and forth in a figure eight. As the video reveals, they can adapt to wind by twisting their bodies to accommodate the air flow, a strategy that burns more energy but lets them continue flying in place. Their nimble wings and tails also help them hold their position, at least enough to keep eating.
Simulated rain also failed to deter the hungry birds. Not only did they seem to ignore the downpour as they fed, but they even paused to shake dry in midair once they'd had their fill. "They shake their bodies like dogs while still flying," researcher Victor Ortega tells KQED, "but they don't lose control."
Editor's note: This story has been updated since it was first published in April 2015.