Rethink of birds' internal compass

To: "Stephen Selden" <>
Subject: Rethink of birds' internal compass
From: knightl <>
Date: Thu, 13 May 2004 21:21:18 +1000

On Thursday, May 13, 2004, at 07:09  PM, Stephen Selden wrote:

Rethink of birds' internal compass

MIGRATING birds may get their internal compass through a chemical
induced by the Earth's magnetic compass rather than through magnetic
material in their beaks as the conventional theory holds.

Its great how they can do it - but we are still wondering how!

- Stephen

Those of you who want to check out the science, may wish to contact the author

Regards, Laurie. n6988/abs/nature02534_fs.html

Nature 429, 177 - 180 (13 May 2004); doi:10.1038/nature02534

Resonance effects indicate a radical-pair mechanism for avian magnetic compass THORSTEN RITZ1, PETER THALAU2, JOHN B. PHILLIPS3, ROSWITHA WILTSCHKO2 & WOLFGANG WILTSCHKO2

1 Department of Physics and Astronomy, University of California,
Irvine, California 92697-4575, USA
2 Zoologisches Institut, Fachbereich Biologie und Informatik, J.W.
Goethe-Universität, Siesmayerstrasse 70, D-60054 Frankfurt am Main, Germany 3 Department of Biology, 2119 Derring Hall, Virginia Tech, Blacksburg, Virginia 24061, USA

Correspondence and requests for materials should be addressed to T.R.

Migratory birds are known to use the geomagnetic field as a source of compass information. There are two competing hypotheses for the primary process underlying the avian magnetic compass, one involving magnetite, the other a magnetically sensitive chemical reaction. Here we show that oscillating magnetic fields disrupt the magnetic orientation behaviour of migratory birds. Robins were disoriented when exposed to a
vertically aligned broadband (0.1–10 MHz) or a single-frequency (7-MHz)
field in addition to the geomagnetic field. Moreover, in the 7-MHz
oscillating field, this effect depended on the angle between the
oscillating and the geomagnetic fields. The birds exhibited seasonally appropriate migratory orientation when the oscillating field was
parallel to the geomagnetic field, but were disoriented when it was
presented at a 24° or 48° angle. These results are consistent with a resonance effect on singlet–triplet transitions and suggest a magnetic compass based on a radical-pair mechanism.

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