On Thu, 11 Jan 1996, Dennis Paulson wrote:
> This is fascinating news. I have also wondered if there might be some
> thermoregulatory function in wing-spreading, and this could easily be
> tested by looking at ambient weather conditions during bouts of spreading.
> Another good research project.

One of Brian McNab's students at U of Florida did a project on wing
spreading and thermoregulation in anhingas. I seem to recall that it
involved measurement of body temp with wings spread and with them folded,
and under different ambient conditions; the conclusion was that having the
wings spread did aid thermoregulation. This was ca. mid-1980s, but I
don't remember the name of the person who did the work.

Of course, merely observing that a structural or behavioral trait has a
thermoregulatory function does not mean that it evolved for [is an
adaptation for] thermoregulation. For example, a comparative physiologist
once measured changes in body T that result when certain antelopes stick
their horns into cool mud. The horns are highly vascular beneath those
keratinous sheaths, and sure enough they were dumping significant amounts
of heat into the cool mud. So he naturally concluded that horns are an
adaptation for [evolved for] thermoregulation...

It will be tough to determine whether wing-spreading was selected for in
the ur-cormorant population to aid in drying wings, thermoregulation, or
both. But it is necessary to make that determination to be able to say what
this trait is an *adaptation* for. In the absence of that determination, we
simply don't know which (if either) of these functions wing spreading is an
adaptation for (or if it is an apation for both of them), only that it has
those functions ("function" does not equal "adaptation").

David Wright
dwright at u.washington.edu