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
reaction
induced by the Earth's magnetic compass rather than through magnetic
material in their beaks as the conventional theory holds.
http://www.news.com.au/common/story_page/
0,4057,9548700%255E1702,00.html
Its great how they can do it - but we are still wondering how!
- Stephen www.envirotalk.com.au
Those of you who want to check out the science, may wish to contact the
author
Regards, Laurie.
http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v429/
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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