Release a pigeon thousands of kilometers from home, and it'll fly across seas, forests, or deserts to return. It's not sight or smell that allows this amazing navigation; migratory birds can sense the magnetic fields that vary across Earth's surface. Now, scientists have identified a collection of brain cells that let pigeons interpret these magnetic fields. They hope the findings will help reveal how the birds sense the magnetism in the first place, and shed light on this mysterious sixth sense.
"This is very exciting," says biologist John Phillips of Virginia Polytechnic Institute and State University in Blacksburg, who was not involved in the new study. "There have been very few clear-cut findings in the past."
Debate on how birds sense geomagnetic fields has largely revolved around magnetite particles found in various parts of their heads. Scientists have hypothesized that magnetite, a form of iron that's the most magnetic of naturally occurring minerals, is the key ingredient in specialized cells that react to changes in magnetism. And the presence of magnetite in birds' beaks had led some researchers to believe that this structure was key to birds' homing abilities.
But earlier this month, a team of scientists showed that the iron in birds' beaks isn't magnetite—it's balls of another, less magnetic, form of iron accumulated in white blood cells that are cleaning toxins out of the animals' bodies."That whole story just crashed and burned," says Phillips.
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