I unpacked the drinking bird, and in response to complaints from the
peanut gallery, adjusted it so it started working again, after the
house-move.
In this currently purchasable incarnation, the bird will bob for
an hour or two if faced with a beaker of warm water, into which
its beak DOES NOT dip. (Radiative heating)
Or if its beak dips into water, water at room temperature - it will
keep stooping to drink until its beak no longer contacts the water
surface. That means 12 hours and more - perhaps indefinitely.
(Evaporative cooling)
This may be old news to you, but I was immensely pleased to see
just how effectively this little heat engine ran on a temperature
differential no more than the psychrometric tables specify.
I can now see much better why a wildcat MIT student engineer
would use propane driving antifreeze to turn a solar panel into the
Sun on a polar mount.