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Birds navigate by Earth's magnetic fields: re -

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Birds navigate by Earth's magnetic fields: research

The World Today - Wednesday, 7 May , 2008 12:37:00

Reporter: David Mark

ELEANOR HALL: It's one of the great questions of nature - how do migrating birds navigate as they
make journeys that are sometimes thousands of kilometres long?

It's known they use magnetic fields, but not how. Now some US scientists say they've discovered the
answer and they have published their research in the journal, Nature.

Professor Devens Gust, from Arizona State University is one of the paper's authors and he has been
speaking to David Mark.

DEVENS GUST: What our work does is show for the first time that magnetic fields like those at the
earth can actually influence the course of chemical reactions.

DAVID MARK: So essentially, the bird may have a molecule in its brain that is interpreting the
earth's magnetic field?

DEVENS GUST: Well, yes except the molecule is probably in the bird's eye since it is light
sensitive molecule and the whole process is actually initiated by light, so the thought is, the
most likely theory is that the molecules are in the eye of the bird and they generate a signal that
is then transmitted to the bird's brain.

DAVID MARK: Do you have any sense of what the bird may be perceiving? How do they see this magnetic
field?

DEVENS GUST: That is something that nobody knows and people can speculate about that but it's
really unknown. Whether they see some special kind of lines or some kind of a spot or something
like that, or maybe it's not even sight at all as we know it but some sort of a feeling of the bird
that it's doing the right thing or not doing the right thing.

Nobody really knows how the signal gets transduced into something the bird perceives.

DAVID MARK: Do you understand the extent to which the birds may be operating using latitude or
longitude, in other words, how they can pinpoint their place on the globe?

DEVENS GUST: Well yeah, there are two aspects to this idea of navigation. One of course is knowing
where you are and the other approach, other aspect is knowing which direction north or south might
be in.

As far as knowing which way north, and knowing where they are, both it can be perhaps addressed by
the angle that the magnetic field lines make with the earth.

It turns out that around the equator, the magnetic field lines are more or less parallel to the
surface of the earth but as you move north or south, then the field lines dip down toward the
earth.

And at the poles they are actually perpendicular to the surface of the earth, so by measuring that
inclination or sensing it, the bird might know its latitude.

DAVID MARK: This is an extraordinary discovery isn't it? Because it answers a question that so many
people have been asking for decades. It's been known that birds can navigate but not how. Do you
feel that you have made a major breakthrough?

DEVENS GUST: Well, yes, it has been known for about 40 years that they can navigate using their
fields and it has been known or suggested about 30 years ago that this particular mechanism we've
been working on, might actually be the way that they do it but there has been no proof over that
whole time period and finally what we have is proof that this mechanism can work.

Again, we haven't shown that it does work in birds but we've shown that it can work in a
laboratory.

ELEANOR HALL: That is Professor Devens Gust from Arizona State University, speaking to David Mark
about that research he has published in the journal, Nature.