Unmasking Owls’ Mysteries

IRA FLATOW: I want to bring you a conversation about a distinctive animal, one that is both a vicious predator and incredibly cute. I’m talking about owls. Here with me is our resident owl enthusiast John Dankosky.

John, why are you so enthralled by owls?

JOHN DANKOSKY: Ah, boy, Ira, I literally drink coffee in the morning out of one owl mug that I have, and I drink tea in the afternoon out of another owl mug. I love these birds. I find them mysterious.

In recent years, too, I’ve been seeing a lot of them in the woods near my house. I love how they can just hunt so silently, but also make really distinctive sounds when they want to be heard. I could go on forever but, needless to say, I really, really love owls.

IRA FLATOW: Yeah. I’ve been always fascinated by them myself, if not a little terrified. I remember once a few years ago, an owl once tried to attack my neighbor’s dog.

JOHN DANKOSKY: Oh, no.

IRA FLATOW: Yeah. And she had to shoo it and muscle it away from flying in. Because they pack so much power into such a small package, don’t they?

JOHN DANKOSKY: Yeah, they really do. And I hope the dog is OK.

IRA FLATOW: Yeah, the dog is OK.

JOHN DANKOSKY: It’s one of the things that really excites me about them as you said they have these beautiful calm just really cute faces, but they are deadly predators. And scientists are learning a lot more about why they’re such good predators– how their hearing and their night vision is so sharp and how their flight is just so quiet.

So here to talk more about all things owls is my guest, Jennifer Ackerman. She’s the author of a new book, What an Owl Knows: The New Science of the World’s Most Enigmatic Birds. She’s based in Charlottesville, Virginia.

Jennifer, welcome back to Science Friday.

JENNIFER ACKERMAN: It’s such a pleasure. Thank you for having me.

JOHN DANKOSKY: The hoot of the owl is probably the most recognizable bird call that we have. But it’s not just hoots that owls make, or shrieks. They’ve got a very sophisticated form of communication. What have scientists learned about how owls communicate?

JENNIFER ACKERMAN: Yeah. Well, they’ve learned that a hoot is not just a hoot. It’s one of the really delightful surprises I learned in my research. Owls have very elaborate vocal repertoires that are really teeming with meaning. They have greeting hoots and territorial hoots and emphatic hoots. And they don’t just hoot. They chitter, squawk, squeal, and their different calls communicate really highly specific information about their sex, their size, their weight, their individual identity, and even their state of mind.

JOHN DANKOSKY: And decoding some of these vocalizations using machine learning has revealed something pretty interesting– that owls might not be as monogamous as we thought.

JENNIFER ACKERMAN: It’s true. And the way we’ve learned this is that it turns out that adult owls have highly distinctive voices. And they can actually recognize one another by voice alone. And now, we, too, can identify individual wild owls living in the woods by these unique territorial hoots.

And that means two things– that researchers can actually monitor these owl populations more accurately– and that is a really important tool for conservation– but also they can actually observe by listening who’s mating with whom and whether couples are in fact staying together.

And the wisdom had been that most species of owls were monogamous, pairs mated for life. And it turns out to be not so. To the great surprise of scientists, there’s often so much mate switching among the owls they’re monitoring that it’s hard to keep up.

JOHN DANKOSKY: There are so many distinctive owl species, and you talk about so many of them in your book. I want to talk about a few of them. And we’ll start with the great gray owl, this iconic bird. It’s really impressive when it comes to its hearing. And one of the facts in your book that fascinated me the most is that they’re able to hear a vole scurrying under a foot of snow. How are they able to do this?

JENNIFER ACKERMAN: Yeah, this was the thing that just blew me away about a great gray owl is, from the air, they can hear a vole or a mouse tunneling under as much as 18 inches of snow. That’s just so remarkable. It was really almost four or five decades ago, in the 1960s, that the famous biologist Roger Payne, he showed that an owl can actually catch a mouse in the pitch black, relying only on sound.

And it turns out, owls that hunt by ear, like barn owls and great gray owls, their heads are really just designed for listening. They have these big facial disks that act like a big feathered external ear. It’s kind of like a satellite dish for collecting sound. And this facial disk channels the sound toward their ears.

And it’s what’s inside those ears that’s really so remarkable. And scientists have begun to tease apart lately. They describe an owls inner ears as the race cars, the Ferraris, of sound sensitivity. And it’s true. Owls have these really big cochlea. They’re the hearing organs in the brain. In a bird like the barn owl, the cochlea is just crazy long. It’s like three or four times as long as the cochlea of most other birds. And that gives barn owls, great gray owls, a sense of hearing that’s really almost unequaled in the animal world.

JOHN DANKOSKY: So they’re very sensitive to sound. They hear very well. But what makes them such efficient predators is then they, like, don’t make any noise. Prey can’t hear them coming. Even the most silent predator birds other than owls, you can hear them flapping down. What is it about owls’ wings that make them so silent?

JENNIFER ACKERMAN: Yeah, I think it’s one of the great wonders of the bird world is an owl’s quiet flight. And they can fly quietly, in part, because they have what’s called low wing loading. And that’s that their wings are very big in relation to their bodies. So their flight is very buoyant and slow. But it’s also because of the really ingenious design of their wings and feathers, which squelch the normal sounds that bird wings and feathers make.

Owls have three really remarkable features that hush their flight. And they have this– it’s called a comb– a row of really fine hairlike bristles that extend forward along the leading edge of the wing, where it meets the oncoming air. And when the air hits that comb, the serrations and those little bristles, they break up the turbulence that normally causes a lot of noise on a bird’s wing. And that effectively suppresses the swoosh sound that usually is made by a bird’s wing.

And then they have that little row of wispy veined fringes on the rear edge of the wing that serves a similar function. And then– this is the really cool thing– they have this soft layer of velvet that coats the feathers in the whole wing. And that silences any rubbing-together noise that the feathers might make in another bird.

JOHN DANKOSKY: Now, owls’ eyesight is also pretty different from other birds. How is it different?

JENNIFER ACKERMAN: For one thing, they have eyes that are really big for their body size. If our eyes were in similar proportion to our bodies as an owl’s eyes are to its body, they’d be about the size of an orange and weigh almost 4 pounds. So owl eyes are super big. They’re also tubular and they’re rigid and locked in their sockets in a forward gaze, like ours are. Their forward-facing eyes gives them binocular vision, which is a really big advantage in zeroing in on moving prey, the way they have to.

But also having your eyes locked in place, that has consequences. Owls can’t move their eyes. So they actually have to move their heads to keep something in sight. It’s a myth that owls can actually rotate their heads full circle, but some species can turn their heads almost 3/4 of the way around. Which is three times the twisting flexibility that we humans have.

JOHN DANKOSKY: I’m John Dankosky, and this is Science Friday, from WNYC Studios.

Let’s talk about another iconic owl species, burrowing owls. And I want to hear where they live and what they do. But could you first describe a burrowing owl for someone who’s never seen one before?

JENNIFER ACKERMAN: Yeah. Well, they are just the most comical, kind of adorable little creatures. They’re just heads on long stilt-like legs. And they have this habit of cocking their heads in curiosity. They’re very cartoon-like and human-like at the same time.

First of all, they live in 24 countries in North and South America. So they’re very widespread in the New World. And they nest underground in burrows that are dug by, oh, prairie dogs, woodchucks, skunks, badgers, and armadillos, and sometimes even under human-made structures. I’ve seen them nesting under piles of debris or little openings beneath pavement.

And one of the really cool things about these little owls that I learned in researching the book is they actually decorate the outside of their burrows with all kinds of stuff, all kinds of treasures– stuff like dung– bison dung or coyote scat. They decorate with bits of wood, bones, moss, and swatches of fabric. It’s kind of like whatever they can find. And they actually have preferred colors of things. They like red and white over blue and green, for instance.

But what was interesting to me is that all this decorating isn’t about mate attraction or courting, the way it is in some birds. Because the male only begins decorating after his mate has started nesting and laying eggs. And the decorations are really meant to convey to other males that the burrow is occupied. So a male is saying, don’t mess with me. I own this place. Look at all this stuff I collected.

[LAUGHTER]

The researcher who studies these birds, David Johnson, said to me, if you want to show you’re a tough guy in the world of burrowing owls, decorate.

[LAUGHTER]

I just love that. I mean, who knew?

JOHN DANKOSKY: What’s it like to be near an owl, to get up close and personal and actually see it doing its owl-y things?

JENNIFER ACKERMAN: Yeah, I think the most exciting experience for me was I was in the field in Western Montana with Denver Holt, who I think is considered probably one of the world’s foremost experts on owls, and I had the opportunity to hold one of these. It was a long-eared owl. And it was just an incredible experience. Because her legs were these big strong legs– these killer talons– tucked between my fingers, but her wings were soft as rabbit’s fur.

And that is the thing about owls– they’re ferocious and also they’re soft and tender. This owl was incredibly cute, but also like a brutal killer. This bird, she kind of locked eyes with me in this cat-like stare. And I just felt like, there we were, eye to eye, creature to creature, and it just felt like such a powerful connection, both of us questioning, what are you? What are you thinking? What are you feeling?

I just held her for a while and marveled at how beautiful she was and how superbly adapted to her world, really, so quiet, so skilled. It was really an amazing experience.

JOHN DANKOSKY: They really are remarkable animals. Jennifer Ackerman is the author of What an Owl Knows. Jennifer, thanks so much for the book and for bringing us all these great stories.

JENNIFER ACKERMAN: Thank you so much for having me here, John.

JOHN DANKOSKY: And if you want to read an excerpt of the book, go to sciencefriday.com/owls.

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