-------------------------------------------------------------
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?)