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National Geographic News: “Birds Can ‘See’ Earth's Magnetic Field”
Imagine it: you’ve gone off-trail in the woods on a moonless night—without any navigational equipment—and now you’re trying to find your way back to camp. You know you’ve generally been traveling in a northwesterly direction, so you simply look around, take a look at the earth’s magnetic field, change your heading to southeast, and march back until you’re in familiar territory.
The idea of taking a look at earth’s magnetic field ... may be more than fantasy for birds.
Sound pretty fantastic? For humans, the idea of taking a look at earth’s magnetic field is just that: fantasy. But according to a new study published in PLoS ONE, such a capability may be more than fantasy for birds.
In the study, a team of German researchers injected migratory garden warblers with a dye that can be tracked while moving through the nervous system. The team injected the dye in the birds’ eyes as well as a region of the brain called Cluster N, known to be active when the birds orient themselves.
The researchers observed dye movement as the birds oriented themselves, discovering that the tracer dyes traveled from the two regions to meet in the warbler thalamus. The thalamus is a region of the brain that helps govern the visual sense (among other things). The meeting of the tracers indicated, according to lead study author Dominik Heyers, that “there is direct linkage between the eye and Cluster N.” Heyers is a biologist at the University of Oldenburg.
Thus, the research supports the hypothesis that birds somehow “see” (use their visual sense) the earth’s magnetic field as they use it to navigate.
“The magnetic field or magnetic direction may be perceived as a dark or light spot which lies upon the normal visual field of the bird,” Heyers said, “and which, of course, changes when the bird turns its head.”
However the birds perceive the field, it’s clear that the system is more sophisticated than the ordinary mariner’s compass! Scientists suspect the presence of specific molecules in birds’ eyes that are able to detect the magnetic field; however, scientists not involved in the study add that “there are more pieces to the puzzle of how birds navigate on their long migrations.” For example, biologist Cordula Mora at the University of North Carolina–Chapel Hill has hypothesized that “birds may use magnetic crystals in their beaks to sense the intensity of the magnetic field and thus glean information on their physical location,” providing them with information not only on orientation (north, south, east, west), but also relative location.
Bird navigation expert Robert Beason, a wildlife research biologist with the U.S. Department of Agriculture, believes birds may even use the stars to find their bearings!
And if that’s not impressive enough, bird navigation expert Robert Beason, a wildlife research biologist with the U.S. Department of Agriculture, believes birds may even use the stars to find their bearings!
Certainly, there are many mysteries left to be solved when it comes to bird navigation. Although we will never know exactly what birds experience, it’s a safe bet that their sophisticated system rivals or exceeds any sensory system scientists have created. It’s just another in a long line (longer than we realize, of course) of amazing design features that, whether we join in or not, extol the creativity of the master Designer.
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