Birds Can Actually See The Earth’s Magnetic Field, Not Just Sense It

By on April 10, 2018
bird

Birds have a pretty great sense of direction. It’s how they’re able to migrate between seasons and how messenger pigeons were trained for use in the past.

But for a long time we’ve believed their navigational abilities comes from iron in their beaks that lets them sense the Earth’s magnetic pull.

As it turns out, it’s not their beaks but their eyes letting them find their way across long distances. Two new studies on robins and zebra finches have shows the birds actually navigate thanks to a special protein in their eyes.

This protein is Cry4, from a class of proteins called cryptochromes. These are chemical photoreceptors sensitive to blue light that are found in both plants and animals. They play an important part in maintaining the body’s circadian rhythm, its body clock.

The new studies proved a possibility scientists have been considering for years, that Cry4 in a bird’s eyes are what let it see magnetic fields, a physical sense called magnetoreception. With this special sight birds can use the direction of Earth’s magnetic fields to navigate over long distances.

A research team from Lund University in Sweden studied zebra finches, while a team from the Carl von Ossietzky University Oldenburg in Germany studied European robins. What they individually found was that, while other cryptochrome levels varied through the day, Cry4 remained constant. They also found that, not only is this protein clustered around areas of the retina that receive a lot of light, they also increase in quantity during migratory season.

However both sets of researchers so far say their work is far from absolute. They indicate that, though the evidence is strong, they’ll need more proof.

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