Hummingbirds zooming around the garden from flower to flower and sipping nectar probably don’t appear at first glance to be models for instruments of war.
But the tiny thrumming birds are unparalleled aerial acrobats, power in miniature, instantly zipping forward and backward, diving quickly down and soaring back up, pitching, rolling and yawing, and even flying upside down. Their sophisticated flying abilities have captured the attention of robot designers, especially those studying the use of drones in modern warfare.
“Hummingbirds are the best flyers out there,” said Bret Tobalske, a biology professor and director of the University of Montana’s Flight Lab. “They are extreme in their physiology and flight performance. They are incredibly manoeuvrable. They are capable of hovering indefinitely” — an adaptation driven by a love of nectar.
As crew-less vehicles have taken over the skies in conflicts, hummingbirds have become the subject of new research. The Flight Lab, accustomed to looking at the ecology, evolution and biomechanics of bird flight, is part of an effort, funded largely by US defence dollars, to build a better robotic hummingbird. Mimicking these birds — a phenomenon known as bio-inspired technology — is the holy grail for the makers of flying robots.
There have been hummingbird robots built — most notably the NanoHummingbird, built by AeroVironment, a private company, with funding from the Defence Advanced Research Projects Agency — but they have myriad limitations. “None of these robots can fly fast forward,” said Dr David Letink, a professor of biomimetics at Groningen University in the Netherlands who has studied and built flying robots for decades. “That can only be performed by bigger robots.”
Aircraft design has long been informed by avian flight. Numerous flight labs study several types of creatures — hawk moths, dragonflies, bats and hummingbirds — to examine the secrets of their flying skills. Much of the work is funded by defence agencies, with the aim of using the knowledge to design better aircraft.
The work at Flight Lab in Montana is funded by the Office of Naval Research, part of the Defence Department, under a contract of a little more than $660,000, part of $2 million over seven years allocated to study the birds. Defence officials did not respond to requests for comment.
A robot based on a hummingbird might not be likely to carry weapons but instead could be deployed to scout streets ahead of troops, spy on troop movements, or be dispatched to search for wounded soldiers in places where humans can’t go, such as inside a collapsed building or a tunnel.
The wings of many hummingbirds beat about 50 times a second, the most of any bird; by contrast, a pigeon’s wings beat nine times a second. Hummingbird hearts, the size of a pea, beat 1,200 times a minute when the bird is active. Human hearts beat 60 to 100 times a minute.
The researchers here are primarily focused on the calliope hummingbird, which weighs less than two paper clips. Yet every autumn, the bird travels a risky migratory path through wind, rain and snow from the Pacific Northwest to southern Mexico.
Much about hummingbird ecology is a mystery, largely because the birds are too small for tracking devices. But they are very transient, Tobalske said. “They spend three months travelling south and three months travelling north again.”
One element of the bird’s dexterity is the way it harvests the inertia from wing thrusts to power its agile manoeuvres.
Tobalske and a doctoral student, Rosalee Elting, have spent years studying the hummingbird’s escape manoeuvres — how it rapidly flees from predators. (He also displayed a photo of a hummer whose escape efforts failed — a praying mantis waiting at a feeder captured and devoured the bird.)
To study escape behaviours, Tobalske and Elting moved towards a bird enclosed in clear plexiglass to frighten it. As it fled, they took high-speed video with cameras developed by the Pentagon to film and study ordnance blasts. That allows researchers to slow the videos down to parse the smallest components of flight.
The birds pitch up and then roll and face away from the feeder and then pitch down and fly away. “It happens in 120 milliseconds, so very short,” Elting said.
She recently embarked on a separate project to unpack manoeuvres that occurred during battles between male hummingbirds as they fended off invaders approaching flowers and feeders in their territory.
The birds are aggressive. Four distinct battle manoeuvres have been identified as the birds hover: chasing and signalling (like charging at an invader); a face-off; spiral flight; and jousting.
Another difficulty is recreating filoplumes that provide sensory input — the tiny, palm-tree-shaped feathers that monitor wind speed, temperature, and the condition of the feathers, then send that information to the bird’s brain.
While many studies examine wing motions, the brain that drives these abilities largely remains a black box. One recent study found that hummingbird neurons are more sensitive to stimuli than those of other species, which helps them process objects faster and enables their nimble flying.
There are other major technical hurdles to overcome for robot makers — short battery life and the sound a robot makes, which would be a dead giveaway that a hummingbird was a robot. Response to sensory information is hard to build into a robot — how a hummingbird reacts to the scent of a flower or the sight of a praying mantis.
Jim Robbins
The author writes for the NYT and elsewhere on the big eco-stories of our time -- climate change, species loss and more
Oman Observer is now on the WhatsApp channel. Click here
