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NOVA ScienceNOW

GPS Pigeons

  • Posted 11.07.12
  • NOVA scienceNOW

We know that homing pigeons can find their way back to their lofts over hundreds of miles of unfamiliar terrain. What we don’t know is how they do it. David Pogue explores competing theories on how pigeons might see, hear, feel, and even smell the landscape below them.

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Launch Video Running Time: 15:15

Transcript

What Are Animals Thinking?

PBS Airdate: November 7, 2012

DAVID POGUE: As my mission continues into the minds of animals, I am about to come face to face with one of the biggest mysteries in animal research.

But first I have to go through security.

JOHN HAGSTRUM: (As Referee) I've been sent here to take all your electronic devices away from you.

DAVID POGUE: Dude, I am my electronic devices. For some reason, these guys don't trust me.

That's it. That's all I've got, dude.

JOHN HAGSTRUM: Oh, ho, well, what's this here.

DAVID POGUE: All right, well, for emergencies.

JOHN HAGSTRUM: Ah, ha. All right.

DAVID POGUE: There's no seats in this van, and there's no windows.

JOHN HAGSTRUM: That's right.

DAVID POGUE: As I am about to discover, all this cloak and dagger action is an effort to level the playing field, so I can compete against one of the animal kingdom's most amazing creatures.

Hey, there's a pigeon back here.

My fellow hostage is a Columba livia, more commonly known as a homing pigeon. She may not look extraordinary, but trust me, she is. And she's got a huge secret.

If you transport pigeons away from their home lofts and release them, they will immediately fly home.

Flying at close to 60 miles an hour, these pigeons consistently complete journeys up to a thousand miles long. That's farther than the distance from St. Louis to New York.

But how do they navigate so efficiently over completely unfamiliar terrain.

CHARLIE WALCOTT: Here is a question: How do pigeons find their way home? Been worked on for many, many years, and yet, it still is a mystery.

JOHN HAGSTRUM: We're here.

DAVID POGUE: Oh, my gosh. Where the hell are we.

JOHN HAGSTRUM: Dave, it's time to explain the rules.

DAVID POGUE: Yeah. I'd love to know what's going on.

And now I'm getting a real taste of the mystery, because this guy, pigeon owner Jim Korineck, is releasing the bird and me in a completely unknown location.

JIM KORINECK: So this is Zipline.

DAVID POGUE: Hello, Zipline.

JIM KORINECK: You're going to be racing a homing pigeon.

DAVID POGUE: The race will cover 60 miles, and the finish line is Zipline's home loft, in Tempe.

JIM KORINECK: Now, we're going to give you all sorts of help.

DAVID POGUE: Oh, you are.

JIM KORINECK: You get a compass.

Yes. And then a set of keys to a car.

Are you ready Zipline.

Go.

JIM KORINECK: If you can get in the car fast enough you can follow her.

DAVID POGUE: Wait.

I don't even know which way to start. Which, which road….

JIM KORINECK: Zipline's done this a lot of times. David doesn't have a chance.

DAVID POGUE: Oh, no. No, no, no, no, no.

At least I still I have my compass. I know that this way is north and this way is south, but wait a second, which way do I go.

I don't know what to do with this thing.

CHARLIE WALCOTT: One would think that a compass might be sufficient, and it isn't, for a very fundamental reason, which is that the compass tells you where north, south, east and west is, but it does not tell you where home is.

DAVID POGUE: All I know is that I'm somewhere in a 60 mile radius of Tempe, Arizona. Before I can figure out which direction to drive, I would first need to know where I am in relation to Tempe.

Since I've never been here before, even if I could find a road sign or a big landmark, I'd need to locate that on a map and then figure out the direction to Tempe.

Scientists know that, just like us, pigeons must navigate using both a compass and a map.

Recent studies show that pigeons can sense the earth's magnetic field and probably use that for their compass.

CHARLIE WALCOTT: The thing that we don't understand is what we call the map: how a pigeon, taken to some place where it's never been before and released, knows where it is with relation to home. That is the fundamental mystery.

DAVID POGUE: The mystery for me is where in the world am I.

Excuse me. Do you know how I can get to Tempe, Arizona.

CHARLIE WALCOTT: I have no idea how to get to Tempe, Arizona. But I'd love a ride.

DAVID POGUE: All right, hop in.

Full disclosure, this hitchhiker is actually a plant. You've met him before. He's Charles Walcott, professor of neurobiology at Cornell and world-renowned pigeon expert.

So I understand you know something about these homing pigeons.

CHARLIE WALCOTT: I've worked with them for 30 years.

DAVID POGUE: That probably gives you qualifications to answer this one tiny question that I've got: how do they do it.

CHARLIE WALCOTT: We don't know.

DAVID POGUE: Well, a lot of help you are.

CHARLIE WALCOTT: One theory is that the pigeons use odors, or smell to find their way home.

DAVID POGUE: It may sound a bit crazy, but scientists in Italy discovered that if you deprive a pigeon of its sense of smell, it won't make it home.

ANNA GAGLIARDO (University of Pisa): I think that pigeons use smell to navigate.

DAVID POGUE: Professor Anne Gagliardo believes that, from a young age, pigeons get their sense of direction from the odors around their home lofts.

ANNA GAGLIARDO: When the pigeons are at their home loft, they learn to associate the odors carried by the wind with the wind direction. And so they build up a sort of map of the environment.

DAVID POGUE: For example, imagine a pigeon knows that in its home loft, the smell of lemon comes from 10 degrees north and the smell of the sea comes from 100 degrees to the east. When they are taken to a release site, they will search for the smell of lemon and the scent of the sea to get the bearings of both and use these to guide themselves home.

I don't think that's going to help me too much. I'm getting mostly, like, desert. I still have no clue which way to go home.

CHARLIE WALCOTT: The problem with the, uh, smell theory is how can you detect odors over distances of, of a hundred miles? And pigeons routinely home from 500 or 1,000 miles away.

DAVID POGUE: So if Zipline's not smelling her way home, how does she do it? Scientists in New Zealand believe that pigeons use the earth's magnetic field, not just for their compass, but for their map, too.

TODD DENNIS (University of Auckland): Well, everything that I've done has pointed to the fact that it is in indeed the magnetic field that, that is the primary candidate for the, the, the pigeon's navigational map.

DAVID POGUE: The earth is completely surrounded by a magnetic field, emanating from the North and South Poles.

But that field isn't uniform around the globe. Whenever it interacts with magnetic material in the earth's crust, for example iron or volcanoes, it bends, creating a magnetic contour map of the world.

Todd Dennis and Michael Walker of the University of Auckland have been studying pigeon navigation for years, and they believe that the birds use this magnetic contour map to find their way home.

To test their hypothesis, they've been taking pigeons miles from their home lofts, strapping lightweight G.P.S.s onto their backs, and then releasing them from different locations.

MICHAEL WALKER (University of Auckland): Now that we can actually record a trek all the way home, we can see this highly detailed responses to the earth's magnetic field at the release site.

DAVID POGUE: What they discovered is that some pigeons seemed to fly off course for the first part of the journey, and then, eventually, took a straighter trajectory toward home.

It was almost as if they were looking for something. Dennis and Walker believe that what they were looking for was the magnetic contour line that ran through their home loft.

Sure enough, when they released pigeons at different locations, each the same distance from home, the pigeons who completed the journey the fastest, were the ones who started out closest to the appropriate magnetic line.

MIKE WALKER: I am reasonably confident that, yes, we have cracked this.

DAVID POGUE: Then, mystery solved. They detect the earth's magnetic field.

CHARLIE WALCOTT: We don't think so.

DAVID POGUE: The reason he doesn't think this totally solves the mystery, is that he has tested the magnetism theory. Walcott constructed special pigeon helmets designed to disrupt the earth's magnetic field. Guess what.

CHARLIE WALCOTT: Well, they could fly straight home. They totally ignore it.

DAVID POGUE: Well, that's two theories shot. So, if it is not magnetism and it is not smell, how do they do it? The answer may lie here, on a hill in upstate New York. It's called Jersey Hill and it's ground zero in the pigeon mystery. For 20 years Walcott released hundreds of birds from Jersey Hill, and most of them ended up getting lost.

CHARLIE WALCOTT: If we release Cornell homing pigeons at Jersey Hill only about 10 percent of them ever come home.

DAVID POGUE: Jersey Hill has no magnetic anomalies, no weird smells—and there is more—only the birds from the Cornell loft got lost. Birds from nearby lofts had no problem.

So if someone could solve the mystery of Jersey Hill, you'd probably finally crack the mystery of the homing pigeon.

CHARLIE WALCOTT: It might well be, because something certainly interesting is going on there, and we really don't understand what it is.

Here comes somebody.

DAVID POGUE: Excuse me, do you know how to get to Tempe.

JOHN HAGSTRUM (United States Geological Survey): No, I'm afraid not. But I can tell you what's going on at Jersey Hill.

DAVID POGUE: What.

CHARLIE WALCOTT: Well, in that case, you can get in.

DAVID POGUE: There's something going on here. You're another plant, aren't you.

JOHN HAGSTRUM: Yeah, I'm afraid so.

DAVID POGUE: John Hagstrum is a geologist, and he's been studying pigeon navigation for decades.

So, let me get this straight. You know about Jersey Hill, these, these homing pigeons who couldn't find their way back to the Cornell nests.

JOHN HAGSTRUM: That's right.

DAVID POGUE: Well, what the heck was going on.

JOHN HAGSTRUM: Well, I think the pigeons are using sound to find their home.

DAVID POGUE: Hagstrum got the idea for his theory when he read about an event called The Great Pigeon Race Disaster. In 1997, thousands of pigeons were released in France, for a race back to their lofts in England. Almost none of them got home in time.

JOHN HAGSTRUM: It turns out that they flew them across the English Channel just as the Concorde, which was leaving Paris, was going supersonic and laying down a boom carpet that these pigeons were caught in.

DAVID POGUE: Hagstrum believes that the sonic boom from the Concorde was so loud that it disrupted the pigeons' navigational system.

So, not smell, not earth's magnetic field, but sound.

JOHN HAGSTRUM: Sound. Infrasound, low frequency sound, below our hearing.

DAVID POGUE: So what exactly is infrasound and why would it be useful to pigeons.

Every minute of every day, massive waves in the middle of the ocean are banging into each other with such force that they actually move the earth's crust one or two microns. That's a tiny amount, but this movement of the earth, as small as it is, generates a huge infrasonic noise.

So these birds are somehow navigating by hearing the rumble of the earth. There's no rumble.

JOHN HAGSTRUM: Well, you can't hear it—it's way below your hearing.

DAVID POGUE: Yeah, I'll say.

JOHN HAGSTRUM: But birds have very sensitive low frequency hearing.

DAVID POGUE: The sound waves you're hearing from my voice, right now, have a frequency around 300 hertz, and the wavelength is under a yard long.

Infrasonic sound coming from the earth's crust is ultra-low frequency sound, and the wavelengths are over a mile long.

These soundwaves travel for thousands of miles, and—here's the key—every place on earth has its own infrasonic signature. It would be as if each house on earth was playing its own radio station.

Experiments have shown that pigeons hear infrasound, and Hagstrum believes that the pigeons know exactly what their home loft sounds like infrasonically, and they use that to guide them home.

But how does this explain why the Cornell pigeons couldn't find their way home? There was no Concorde jet flying in the neighborhood.

JOHN HAGSTRUM: I think Jersey Hill was in a sound shadow, relative to the Cornell loft.

DAVID POGUE: Hagstrum studied the atmospheric conditions on the days that the Cornell pigeons got lost, and according to his calculations the sound from the Cornell loft would have bounced right over Jersey hill, but not the sound from the other lofts.

So, Charlie, maybe it's not smell and it's not magnetic fields. Maybe it's sound.

CHARLIE WALCOTT: Maybe. But again we need some more experiments to be sure.

DAVID POGUE: So you have some more work to do before you know for sure.

JOHN HAGSTRUM: A lot.

DAVID POGUE: All right, so we'll call you back in a week or so.

JOHN HAGSTRUM: Uh, I'd say in a year or two.

DAVID POGUE: So, will it turn out to be sound or magnetism or smell.

CHARLIE WALCOTT: I think one of the major mistakes that people make is to think that there's one solution to the problem. It's really like the issue of how you find your way home. You use a variety of cues, and I think the same thing is true with pigeons.

DAVID POGUE: All kinds of things happen to pigeons: dogs, sonic shadows, you just don't know.

Stop the clock! I'm here. Where are you.

Oh, hello. So you made it back here a couple minutes before me with your stacked deck and your unfair natural advantage! All right, well done this time, buddy, but let's see you host a TV show.

During WWII, the same government agency that developed the atomic bomb was also secretly planning…
PROJECT PIGEON
Pigeons were trained to ride inside missiles and guide them…
by pecking on a screen.
In 1944, the project was cancelled in favor of other secret research…
…into radar.
Lucky pigeons!

Credits

What Are Animals Thinking?

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David Pogue
WRITTEN, PRODUCED AND DIRECTED BY
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Laurie Santos Profile

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Tobey List

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NOVA scienceNOW is a trademark of the WGBH Educational Foundation

NOVA scienceNOW is produced for WGBH/Boston

This material is based upon work supported by the National Science Foundation under Grant No. 0917517. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

© 2012 WGBH Educational Foundation

All rights reserved

Image

(pigeon)
© wepix/iStock

Participants

Todd Dennis
University of Aukland
Anna Gagliardo
University of Pisa
Jon Hagstrum
USGS
Jim Korinek
Pigeon Owner
Charles Walcott
Cornell University
Mike Walker
University of Aukland

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