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David Wright wrote:

> Bird wings do have arteries and veins.  As Brad alluded, these vessels
> are not generally set up for serious heat transfer (e.g., rete mirabile)
> in birds (anhingas in particular?).  A spread wing should absorb heat
> better across its total surface better than a folded wing

Well, the [very small] part of the wing that is covered in skin has blood
vessels, permanently.  However, the vast majority of the surface area of
the wing is formed by the remiges or flight feathers.  These feathers have
blood vessels only when they are growing.  A set of mature feathers,
however, is completely inert.  Dead.  The dermal pith inside the feather
shaft is resorbed when growth is completed, and the inferior umbilicus
(the pore that allows connection of the growing feather with the skin and
circulatory system) is sealed off with a plug of keratin.  Nothing inside
the feather shaft except air after that.  After molt is completed, the
feathers are not set up for ANY heat transfer.  So, unless an Anhinga
always has some growing wing feathers (certainly not the case), the wing,
itself, is not acting as a radiator or heat collecter (unless you're
talking about some bare areas near the armpit).

Kenn Kaufmann (1996, Lives of North American Birds) says that both
cormorants and anhingas dry their waterlogged wings after diving.  I seem
to have misplaced my copy of Ehrlich, et al. (Birder's Companion), but I'm
sure somebody out there has it handy.  I'll bet they say the same thing.

Brad
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Brad Bergstrom, Ph.D., Professor           TEL  229-333-5770 /-5759
Department of Biology                      FAX  229-245-6585
Valdosta State University                  e-mail: [log in to unmask]
Valdosta, GA 31698-0015                    Home: 229-333-0743
           Home Page-- http://www.valdosta.edu/~bergstrm/
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