RE: Homing Pigeons? Try Homing Crocodiles...

[John Scanlon <riversleigh@outbackatisa.com.au>]

Dann Pigdon wrote:

> ... signals sent by cryptochromes in the eyes of garden warblers are
processed by the optic lobe in the brain:
 
 http://www.abc.net.au/news/stories/2007/09/27/2044505.htm
-------------------------------------------------------------

And we might thus imagine that birds do indeed 'see' the magnetic field,
perhaps as 'lines of force' projected onto the visual field. But earlier,
Dann also said this was 

> not something you'd expect in largely nocturnal crocs

and I beg to differ: if there's something like a virtual heads-up display of
lines of force it would be much more accessible (contrasting with the visual
background) at night, when it would also be more useful (migratory birds do
a lot of night-flying, do they not?)

John
 
-----------------------------------------------
Dr John D. Scanlon, FCD
Palaeontologist, 
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
AUSTRALIA
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au
http://tinyurl.com/f2rby


> -----Original Message-----
> From: Dann Pigdon [mailto:dannj@alphalink.com.au]
> Sent: Saturday, September 29, 2007 6:34 AM
> To: dinosaur@usc.edu
> Subject: Re: Homing Pigeons? Try Homing Crocodiles...
> 
> 
> 
> "Mickey Rowe;893-2446" wrote:
> >
> > Dann Pigdon <dannj@alphalink.com.au> wrote:
> >
> > > There's no reason to suspect that the homing abilities of birds and
> crocs
> > > are due to the same physiological adaptations - especially since it's
> now
> > > been shown that birds can see magnetic fields via adaptations in the
> eye
> > > itself (not something you'd expect in largely nocturnal crocs).
> >
> > Two things of import... first a quasi-philosophical issue... it is
> > probably not correct to say that birds "see" magnetic fields.  The
> > fact that light receptors in their eyes appear to be involved in
> > magnetic field detection doesn't make that detection anything like
> > vision and hence seeing.
> 
> The latest neurological research by German scientists has shown that
> signals
> sent by cryptochromes in the eyes of garden warblers are processed by the
> optic
> lobe in the brain:
> 
> http://www.abc.net.au/news/stories/2007/09/27/2044505.htm
> 
> --
> ___________________________________________________________________
> 
> Dann Pigdon
> GIS / Archaeologist              geo cities.com/dannsdinosaurs
> Melbourne, Australia             heretichides.soffiles.com
> ___________________________________________________________________