What Color Is North?

How birds and other animals travel so far so accurately. /

Second to the right, and straight on till morning” is one of the most famous navigational instructions in English literature. It is also famously nonsensical. “Second” what? “To the right” from where? What happens if I depart in the morning? Even young Wendy recognizes Peter Pan is just winging it with these instructions. Ambiguous and subjective directions may be fine for visiting lands of pure imagination, but in the real world you need concrete and constant references to navigate well.

Peter is not the only one who needs to fly long distance; migratory birds travel thousands of miles twice a year to find adequate food. But they probably aren’t doing so the way we’d think: They may sense magnetic fields. Birds obviously can’t navigate by line of sight, since their destination is beyond the horizon when they begin. In theory, they could just remember the route and pass it down from parent to fledgling. The unique sights, sounds, or smells of different regions could serve as landmarks along the route. Since their destinations are not as narrow as a single building the way ours often are, the route does not need to be demarcated precisely. Still, landmarks and landscapes can change, especially in the era of human development. While some birds have stopped migrating because humans have made it unnecessary, the ones that still do aren’t getting lost just because we put up our parking lots.

Another landmark available to birds is the Earth’s magnetic field. That field is relatively stable and strongly directional, which makes it useful for orienting one’s self. Biologists like Dmitry Kishkinev have modified and disrupted the navigation and migration behaviors of different bird species with artificial magnetic fields. In some cases, the birds can be made to follow a migration route from a different part of the world just by recreating the Earth’s magnetic field from that region. Recreating other sensory features of those regions did not have the same effect. This evidence leads scientists to believe that at least some birds can sense magnetic fields just like we sense light or sound.

In fact, birds may actually be able to see those magnetic fields. There is a light-sensitive protein in the eyes of birds that reacts to magnetic fields in a way that could generate a nerve signal. Since that signal would be carried to the bird’s brain by the optic nerve, it would likely be perceived visually. We may never know exactly what magnetic fields look like to birds, but I imagine a version of what you or I see enhanced with something like an extra color.

The magnetic field isn’t the only reference point for birds when they navigate. Homing pigeons apparently also use the position of the sun when it’s out. While the sun isn’t fixed, it moves in predictable ways that facilitate reliable orientation. Pigeons that know the time can use the sun to navigate, while pigeons whose internal clock has been artificially confounded go the wrong way—presumably because they misjudge where the sun ought to be relative to the Earth.

At night, the moon and the stars can also provide necessary “land” marks. And birds aren’t the only ones using them. Dung beetles can use the Milky Way in the night sky to keep themselves moving in a straight line. Keeping on a straight path is crucial to the beetles as they roll dung away from where they found it; it minimizes the risk that the ball of food they worked hard to collect isn’t stolen by others hanging around the source. To demonstrate that they specifically use the Milky Way, researchers had the beetles roll dung around in a planetarium where they could control what was in the night “sky”—a clever solution but probably a tough sell to the planetarium director! Eric Warrant, one of those clever and persuasive biologists, noted that this “complicated navigational feat” is “quite impressive for an animal that size.”

You don’t need to soil a science center to observe another nocturnal navigation solution. Moths and other flying insects often circle campfires, porch lights, and other manmade sources of illumination. Their navigation instincts may assume that the brightest object in the sky is very far away, so that when they fly over a relatively short distance in a straight line, their orientation relative to that light shouldn’t change. If it does change, they need to turn to stay on the straight and narrow. For a long time, this assumption would have worked fine because the brightest object would have been the moon. But now it might be a nearby streetlamp. If this theory is correct, as the moth flies near the lamp, it would sense that its orientation relative to the light has changed and so it would turn to correct in a way that would keep it going straight if the lamp were the moon, but instead keeps it going in circles.

We use many of the same tricks the birds and beetles use. Compasses make the magnetic field of the Earth visible to us so we can use it to get around. We know that the sun rises in the east and sets in the west, providing some basic orientation references. Instead of one moon, we imagined a whole array of artificial “moons”—satellites whose locations we know at any given time. Instead of following the invisible magnetic field of the Earth, we receive invisible electromagnetic signals from those satellites, which we see with our GPS receivers and smartphones. Some days it may all seem like fairy magic, but these technologies still rely on the same basic principles that have always governed navigation. We may be more precise, but we’re not doing anything fundamentally different from what animals have worked out.

What does set us apart from our avian counterparts is that we don’t live on bread alone. While birds migrate and beetles roll to keep their stomachs full, we are seeking sustenance for our spiritual hunger as well. So if birds, equipped by special navigational senses, are enabled to find food when they need it, then surely our Father knows of the human need for spiritual direction. “But seek first his kingdom and his righteousness, and all these things will be given to you as well” (Matt. 6:33).

Andy Walsh (@MadroxDupe42) is chief science officer at Health Monitoring Systems, Inc., a public health software company. Among his earlier articles for The Behemoth was a piece on ant travel.

Follow The Behemoth on Twitter and Facebook.

Also in this Issue

Issue 52 / July 7, 2016
  1. Editor's Note from July 07, 2016

    Issue 52: Dreams, animal GPS, and astronaut churches. /

  2. What Dreams Are Really Made Of

    Why we’ve always tried to find transcendent meaning in an ordinary, everynight event. /

  3. Bless Thou the Astronauts

    How the church shaped early lunar exploration. /

  4. A Dream Song (II)

    “The stars are spinning their threads.” /

  5. Wonder on the Web

    Issue 52: Links to amazing stuff.

Issue Archives