Doug Hudson:
>I may be splitting hairs here but I suspect the test performed by R. Payne
>in 1971 gave the owl little chance of catching the mouse. By putting the
>owl in a dark room there was no IR by which the owl could see. It seems to
>me that Mr Payne was testing the owls ability to detect heat which is at a
>longer wave length than near IR.

"IR" is an ambiguous term. Doug is using it in a sense consistent
with the usage in photography - people ask "can I photograph heat
leaking out of my house with B&W IR film?" all the time.

"No" - for the reasons Doug gives (it is sensitive to near-IR, not
"real" IR or heat radiation).

Yet the IR sensors used to steer a missle to a fleeing fighter
jet do indeed read heat radiation.

It is clear that the experiment does as Doug says - determined the
owl could not see down to the wavelength of heat radiation. Since
the researcher knew he'd removed all light sources, I suspect he
knew he wasn't measuring for detection of near-IR which after all
is just reflected light. But his use of the "IR" word is consistent
with usage elsewhere. After all he didn't say "near-IR". So it
sounds to me that he knew what he was testing for and knew what
to call it...

- Don Baccus, Portland OR <donb at rational.com>