At 09:36 06 July 2004, Marian_Aldenhövel wrote: (snip)

will likely notice a change in pressure, even if not
as small a
change as the bird. But we are rarely able to tell
which way, much
less relate the relative change in pressure to absolute
change in
altitude.

We can detect which way the pressure is changing but
the rate of change has to be large for us to do it.
( Hold nose on way down and blow to push the eardrum
out as pressure increases and hold nose and swallow
when climbing, and before someone says that is not
a good thing to do I know. Birds appear much more sensitive
to the change in pressure.

Designing an experiment where one can make sure the
bird translates
pressure change to altitude seems hard to me.

I don't think anyone was saying that birds use the
pressure change to measure altitude, as an altimeter,
but they do appear to use it as we do a vario. I don't
think birds worry whether they are at the correct flight
level or above transition altitude even. A vario works
by measuring small changes in air pressure.

Ciao, MM
--
Marian Aldenhövel, Rosenhain 23, 53123 Bonn.
Fon +49 228 624013, Fax +49 228 624031.
http://www.marian-aldenhoevel.de
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zu!'