Re: Life of Birds (vertical running)

[Graydon <graydon@dsl.ca>]

On Tue, Oct 09, 2001 at 06:43:46PM -0700, Michael de Sosa scripsit:
> David M. wrote:
> >I'd also like to claim that this behaviour requires that the
> >wingstroke has already evolved and therefore does not explain it.
> >I'll stop here and wait for the paper, of course... :.-(
> 
> From what I understand, the wingstroke here is not exactly the same as
> the one used in flying, but advanced non-avian theropods can make both
> motions.  So I suppose that still needs to be explained.

If modern, flying birds can do both -- the stick-to-the-tree one, and
the flight one -- there's no morphological change required.

The flight wingstroke is what you get when you run up a tree that isn't
there, I'd expect.

As for the wing stroke, running away up steep things is a good strategy
for a small cursorial critter; the steeper the thing, the better, too,
so there's a good gradient there for natural selection to work on, given
the existence of feathers on the arms.

-- 
                           graydon@dsl.ca
               To maintain the end is to uphold the means.