Every year millions of migratory birds fly towards their wintering quarters and come back in next year´s spring to breed. Behavioral experiments have shown that the Earth´s magnetic field is the main orientation cue on their journeys.

Nevertheless, surprisingly little is known about the neuronal substrates underlying these navigational abilities. In recent years, it has been suggested that sensing of the magnetic reference direction involves vision and that molecules reacting to the Earth´s magnetic field in the birds’ eye form the molecular basis for a vision-dependent compass mechanism.

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It’d be cool to see magnetic fields, but we humans seem to lack that facility. At least we still have polarized light.