Birds can see Earth`s magnetic field

Last Updated: Tuesday, July 13, 2010 - 18:30

London: Birds can see the Earth`s magnetic
fields through their right eye and use that information to
navigate effectively, German scientists have discovered.

Researchers at the Goethe-Universitat in Frankfurt
found that a bird cannot navigate properly if its right eye is
covered, but it won`t have any problem if the left eye was
covered instead.

Earlier studies had suggested that birds can sense
magnetic fields and use them to navigate, particularly when
migrating south for the winter.

But the latest research found the bird actually sees
the magnetic fields with their right eye giving information to
the left side of their brain.

The magnetic sensing overlaid over the normal vision
with the magnetic fields creating light or dark shadings over
what the bird usually sees.

"The shadings change as the bird turns its head,
giving it a visual compass from the patterns of shading," the
Daily Mail reported.

Scientists believe that the birds have molecules in
their retina which shift into an active state when struck by
blue light in which each molecule has an unpaired electron,
creating a "radical pair".

"The presence of magnetic fields affects the time it
takes for the radical pair molecules to revert to their
inactive state.

"Both the visual and magnetic images involve
variations in light and shade, but visual images tend to have
sharp lines and edges, while the magnetic images have more
gradual changes from light to dark," the report added.
Researchers led by Katrin Stapput discovered that when
this magnetic sense is distorted the patterns of light and
dark make little sense because the bird cannot separate the
information from the visual and magnetic images.

Stapput decided to test the theories by fitting robins
with goggles that were covered with clear foil on one side and
frosted foil on the other.

Both sides of the goggles were equally translucent,
allowing 70 per cent of the light to get through, but on the
frosted side the image was less clear. The birds were then
kept in cages until it was time for them to migrate.

The birds were released into a funnel-shaped cage with
its walls painted with fluid, which was scratched if the birds
touched them.
The results were that birds with no eye coverings, and
birds with the left eye covered set off in a northerly
direction as expected, while those with the right eye covered
were disoriented and headed in random directions.

PTI



First Published: Tuesday, July 13, 2010 - 18:30

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