Is this the basis of Bird Navigation?

04 May 2008
Posted by Chris Smith.

Scientists have shown how birds might be able to see the Earth's magnetic field, helping them to navigate.  A team from Oxford University and Arizona State University, writing in this week's Nature, have uncovered a chemical trick that could enable some animals to see magnetic fields.

Female Mallard in flightPeter Hore and his colleagues studied a molecule containing three key chemical groups, a carotenoid (C), a porphyrin ring (P) and a fullerene (F); this was chosen to mimic the behaviour of some of the light-sensitive pigments found in the retina.  Using this molecule the team found that when they shone light of a certain wavelength at it, the CPF produced a pair of chemicals called free radicals, one at each end of the molecule.

Normally these free-radicals would quickly recombine and cancel each other out, but when the team applied a magnetic field similar in strength to the Earth's magnetic field, a quantum property of the radicals known as their electron "spin" was altered.Now, instead of spinning in opposite directions, known as anti-parallel spin, the electron spins because matched and this significantly affected how long the radicals took to cancel each other out.

"This could trigger a chemical in the eye to change shape, which could in turn kick-start other biochemical processes to enable a bird to see the Earth's magnetic field," says Hore.  Birds could use this information as a reference frame to aid their navigation when visual cues aren't available, such as at night, and during flights over the ocean.

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