thank you for the pointer. That’s a fascinating topic indeed! By the way, from reports here in Germany (and at news@nature I’ve learned that the orignal paper is open-access at PLoS One (DOI: 10.1371/journal.pone.0000937, direct link here.).

I don’t know more about this specific results on “magnetic vision” than from the news reports, but the work of the Oldenburg group goes back to research of biologists at “my” University in Frankfurt am Main.

And a different ascpect of these investigations on magnetoreception in migrating brids that is boosting these days is the investigation of this sense in pigeons. Pigeons have in their beak ferromagnetic crystallites of the iron oxides magnetite and maghemite, and this is thought to be important for their reception of magnetic fields, which could help to explain their navigational skills - see e.g. “Homing pigeons can use magnetic cues for locating food.” by Peter Thalau, Elke Holtkamp-Rötzler, Gerta Fleissner and Wolfgang Wiltschko (Naturwissenschaften 94 (2007) 813; DOI: 10.1007/s00114-007-0259-6) and “A novel concept of Fe-mineral-based magnetoreception: histological and physicochemical data from the upper beak of homing pigeons.” by Gerta Fleissner, Branko Stahl, Peter Thalau, Gerald Falkenberg and Günther Fleissner (Naturwissenschaften 94 (2007) 631; DOI: 10.1007/s00114-007-0236-0).

The physical mechanism that may be at work in the pigeons’ beaks is investigated by physicists at the FIAS - including my senior advisor! Two recent papers by them are “Theoretical Analysis of an Iron Mineral-Based Magnetoreceptor Model in Birds” (Ilia A. Solov’yov and Walter Greiner, Biophysical Journal 93 (2007) 1493; DOI: 10.1529/biophysj.107.105098) and and the arxiv “Towards understanding of birds magnetoreceptor mechanism” (arXiv:0704.1763v1).

All this is really fascinating!

Best regards, Stefan

Some species have 4 or more types of photo receptors. (Also, there are women who can have 4 due to a mutation on an X-chromosome.) This adds resolution and seeing into the UV spectra. White flowers have different colors for pollinating insects.

Likewise insects may see polarized light, an additional experience of information that may resemble the overlay from magnetic receptors. As many people have an accidental ability to perceive it too, we can get a sense for how it feels without having to use computer overlays.

Rupert Sheldrake has had similar thoughts on this topic.

“Numerous experiments on homing have already been carried out with pigeons. Nevertheless, after nearly a century of dedicated but frustrating research, no one knows how pigeons home, and all attempts to explain their navigational ability in terms of known senses and physical forces have so far proved unsuccessful. Researchers in this field readily admit the problem. ‘The amazing flexibility of homing and migrating birds has been a puzzle for years. Remove cue after cue, and yet animals still retain some backup strategy for establishing flight direction.’ ‘The problem of navigation remains essentially unsolved.’

Many of academics might have steered clear because of the the thoughts and subject he has about this? It seems to me that if this information is credible then some of Rupert’s work has some substance to it and hence, brings some credibility to the academic outlook.

[...snip...longer remarks cut out... sorry...too long for so far off-topic. -cvj....]

According to an article by Charles Walcott, et al; “Pigeons Have Magnets,” Science, 205:1027, 1979, “… Homing pigeons seem to possess at least two direction sensors. Years of experiments with released birds have proved that they use sun compasses on sunny days but have magnetic backups for cloudy days. But how do they sense the earth’s magnetic field? Paired-coil tests suggested that the pigeon compass resided in the neck or back of the head. Narrowing the search with sensitive magnetometers and two dozen dissected pigeons, the authors discovered tiny bits of tissue containing magnetite crystals. The same tissues contained yellow crystals likely made by the iron-storage protein ferritin, which was probably used in the biological synthesis of the magnetite. …”.

In Science Frontiers #9, Winter 1979, William R. Corliss added the comment: “Many species of mud bacteria also synthesize magnetite for purposes of orientation, indicating that nature or some directive force used the same strategy in two widely separated species.”

Jon Dobson and Tim St. Pierre at the University of Western Australia have a web page at http://www.biophysics.uwa.edu.au/magnetite.html that says: “… Biomineralization of ferrimagnetic magnetite is known to occur in a number of organisms including animals … Recent investigations have revealed the presence of biogenic magnetite in human brain tissue as well … we are examining tissue samples using scanning and transmission electron microscopy (SEM and TEM), electron energy loss spectroscopy (EELS) and energy filter TEM (EFTEM) imaging in order to locate the particles in the tissue and determine their relationships to structures in the brain. The presence of ferrimagnetic material in human brain tissue also provides plausible theoretical mechanisms for the interaction of environmental magnetic fields with the human central nervous system …”.

Kobayashi, Kirschvink, and Nesson, in Nature v.374, p.123, 9 March 1995, say “… A simple calculation shows that the mechanical energy present in a single 0.1 um magnetite crystal exposed to a 60 Hz, 0.1 mT magnetic field is many times the thermal background noise. Such particles, if adsorbed on cell surfaces or ingested by the cells, could conceivably transfer this energy to contiguous cell structures such as mechanically-activated ion channels (which operate with a gating force close to the thermal noise limit), and thereby alter cytoplasmic ion concentrations …”.

Tony Smith