Wednesday, July 14, 2010

Birds navigate by being able to SEE Earth's magnetic field with their right eye

Snow geese head off on the migratory journey: Scientists have found that birds can actually see magnetic fieldsBirds use their right eye to see the Earth’s magnetic field and use it to navigate, scientists have discovered.

German researchers found that if a bird’s right eye was covered by a frosted goggle, the birds could not navigate effectively, while they could navigate perfectly well if the left eye was covered instead.

It has long been known that birds are able to sense magnetic fields and use them to navigate, particularly when migrating south for the winter.

Now researchers have found that the bird actually sees the magnetic fields with their right eye giving information to the left side of their brain.

The magnetic images create light or dark shadings over what the bird usually sees with its normal vision.

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

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.

Researchers led by Katrin Stapput of Goethe-Universitat in Frankfurt, Germany, 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 percent 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.

via Birds navigate by being able to SEE Earth's magnetic field with their right eye | Mail Online.

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