The Superb Owl and Nature's Stealth Wisdom

The Super Bowl is today, but why not first learn about the superb owl, and what they have to teach us about the ingenious wisdom of evolution.

Thank you for reading The Garden of Forking Paths. I posted a previous version of this essay two years ago, but most of you haven’t seen it, and owls are always wonderful. If you’d like to support my work, please consider upgrading to a paid subscription—it’s just $4/month and it makes this all possible. And Happy Superb Owl Sunday!

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It’s Super Bowl Sunday today—and the bird team is hoping to win. For now, though, it’s time for the Superb Owl to shine, a bird that can teach us much about how to solve pressing human challenges, from flight to clean energy technology.

Ex Uno Plures

Nature guards many fascinating secrets.

Next time you’re on a walk, pause and look at the plant and animal life around you. Then, marvel at the fact that everything you see emerged, slowly but steadily, as evolution’s children, the descendants of tiny, single-cell organisms that lived billions of years ago.

America’s motto is E Pluribus Unum, or Out of Many, One. Nature is the opposite: Ex Uno Plures, or Out of One, Many. We all started as a single organism and have since exploded into an endless, strange supply of innovative life forms.

From the grand experiment that is the vast stretch of evolutionary time, natural forces have carved out some ingenious solutions to challenging problems. Too often, we fail to learn their lessons.

To see why that matters, let’s turn to one extraordinary branch of natural wisdom in the form of owl stealth, a biological engineering innovation that has much to teach us for human technology.

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The evolution of flight and superb owl hearing

The ability to fly has evolved at least four times in life’s history: in birds, bats, pterosaurs, and insects. Gliding, as with the flying squirrel, is one of evolution’s much more common tricks. But it’s more difficult to propel yourself into the air, which is known as powered flight.

Owls, of course, are some of the lucky creatures that can fly under their own power. But the way they do it is extraordinary—and largely unique in the animal kingdom.

Birds have long been useful for human innovation with flight. The Wright Brothers observed birds for years, eventually helping them to create the Wright Flyer. Such innovations are now known as biomimicry, in which humans try to recreate nature’s inventions for our own use. (If you’ve ever used velcro, for example, it was inspired by the tiny hooks on those annoying burs that stick to us when we walk through forests).

If you’re lucky enough to witness the flight of an owl at night, you’ll be struck by how quiet it is. They can fly incredibly close to you, and still, you’ll only sense the slightest whoosh. You’ll be hearing the movement of air more than the flapping of wings or the rustling of feathers. Owls are nature’s stealth planes.

“Nocturnal owls produce about 18 decibels less noise than other birds at similar flight speeds due to their unique wing configuration,” according to Xiaomin Liu of Xi’an Jiaotong University in China. Because the decibel scale is nonlinear and logarithmic, that is a huge difference in noise. And there’s a good reason why owls have evolved that near-silent flight: to help them survive.

There are two main hypotheses for why owls have developed stealth flight. The first is sometimes known as the stealth hunting hypothesis. The idea is simple: it’s easier to catch prey if you can silently swoop down and catch them, all before the unsuspecting vole is even aware of the owl’s presence.

This chart from Knowable Magazine shows how hard it is for humans to detect an owl in flight. Humans can only hear sounds that are above the dotted line. What this chart shows is that much of the time, we can only hear an owl approaching when it comes within one meter (3.3 feet).

Conversely, the prey detection hypothesis inverts that idea, suggesting that owls are minimizing noise so that they don’t undercut their own incredible sense of hearing. With experimental research, in which scientists trained owls to respond to sounds, it quickly became clear that owls have some of the best hearing of any species on the planet, able to register sounds 20 decibels quieter than even the most perceptive human.

According to Christine Köppl, a professor at Carl von Ossietzky University in Oldenburg, Germany, part of that hearing ability is derived from their striking face shape. If you look at a barn owl, for example, you’re effectively looking at a sound collecting dish, which amplifies soundwaves, making them easier to detect in their highly sensitive ears. Astoundingly, when researchers have trimmed back the feathers around an owl’s ruff, their sound detection ability plummeted, converging toward human levels of auditory sensitivity.

However, none of this would be of much use if the overwhelming sound they heard was the beating of their own wings. Because owls are able to detect potential meals by, say, hearing their scurrying feet in the snow from quite some distance, the owl’s flapping feathers could drown out those subtle sounds.

Both theories agree on one core idea: silent flight helps an owl survive because it helps them catch food. And according to recent research by Krista Le Piane of UC-Riverside, it appears that both hypotheses are correct; it just depends on the species of the owl.

How owls fly with stealth technology

Nigel Peake, from the Department of Applied Mathematics and Theoretical Physics at Cambridge University, has been working on understanding owl wings, with research funded partly by the US Navy. Here’s how they describe the mechanics of how the wing works, which they discovered using high resolution microscopy:

The flight feathers on an owl’s wing have a downy covering, which resembles a forest canopy when viewed from above. In addition to this fluffy canopy, owl wings also have a flexible comb of evenly-spaced bristles along their leading edge, and a porous and elastic fringe on the trailing edge.

Here’s a high-resolution of an owl’s flight feather:

“No other bird has this sort of intricate wing structure,” Peake explains. “Much of the noise caused by a wing—whether it’s attached to a bird, a plane or a fan—originates at the trailing edge where the air passing over the wing surface is turbulent. The structure of an owl’s wing serves to reduce noise by smoothing the passage of air as it passes over the wing—scattering the sound so their prey can’t hear them coming.”

This structure has long been baffling and inspiring engineers who see it as a key to unlocking innovation in human technology, from quieter planes to more efficient wind turbines.

Harnessing the secrets of owls for human technology

In the 1930s, a British pilot and bird enthusiast named Robert Rule Graham studied owls and developed a series of theories that are still widely accepted today about owl stealth. Graham used his findings to develop several technological advancements in the new sector of aviation. Those advancements helped make airplanes safer, more reliable, and more efficient. Ironically, he was killed in action while serving on a French warship off the coast of Norway during World War II, which was struck by a bomb dropped by a Nazi warplane in May 1940.

Since then, owls have provided major inspiration in a variety of fields.

Nigel Peake’s research team at Cambridge, for example, is working on a new coating inspired by owl wings that could make computer fans, wind turbines, and aircraft wings significantly quieter.

Siemens Gamesa has already adapted some of its wind turbines, drawing on lessons from owls to reduce noise on the blades. This technology could ease more widespread adoption of wind power, reducing the sound profile for those who live nearby.

Even more important, researchers have been working on ways that they could harness nature’s owl technology to create more efficient wind turbine blades.

And, while it’s still somewhat secretive, owl stealth is being used in government research to determine how to make surveillance craft more silent, including drones and submarines, according to Jackie Higgins in her book Sentient.

The bigger lesson goes well beyond owls. Nature has been engaged in a multi-billion year experiment, in which trial-and-error approaches through evolution have created astonishingly effective ways of overcoming life’s challenges.

We should devote more energy to harnessing those ready-made solutions. Evolution, you’ll be pleased to note, doesn’t care about intellectual property rights.

For example, fresh research that draws on mosquito technology is being used to make better surgical needles. As self-driving cars become more plausible, researchers are turning to the efficient movement within ant colonies to understand how to avoid gridlock. Stronger adhesives are being developed, derived from mussels. Airplane black boxes are becoming more indestructible due to innovations that were inspired by the shock-resistant skulls of woodpeckers.

We’re also using nature’s solutions to save other animals from us. A new kind of glass is being made that, in the eyes of a bird, looks like a spider web. With it installed, the number of collisions between birds and windows plummets.

Though we too often forget it, we are animals, and we face some of the same challenges as our furry and feathery counterparts. Rather than always trying to develop our own wisdom, we should pay more attention to nature’s solutions. Sometimes, as with the magnificent, dare I say superb owl, better ideas are already there, just waiting in the wings.

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