Re: MY THOUGHTS ON THE 'DINO/BIRDS'

[Ronald Orenstein <ornstn@inforamp.net>]

>You may be right with Caudipteryx, its tail is rather similiar to the 
>some of the fan tails found in colies and some "piciformes" (and 
>Sandcoleiformes) that might be for display.  However, nothing says that 
>the tail didn't bear a slight aerodynamic function perhaps related to 
>arboreality.  

True enough - of course no living bird has a long flexible tail.  I wonder how
rigid the tail of Caudipteryx was?  I still find it hard to believe that
such a
short-winged creature could have flown or glided (though Protarchaeopteryx
might have done, I suppose).  I am not familiar with the Sancoleiformes - a
fossil taxon, I presume?

>I still cannot find any logic within the "fluttering" model that was 
>made by Caple et al.. I go along with Rayner (1991) who says: 

Do you have the reference for Caple?  Gee, someone else thought of this
too....

>"...are implausible, for two reasons.  First, there are no comtemporary 
>analogues of running animals feeding with their wings, or using 
>forelimbs as lifting surfaces for stability: running birds generally 
>fold their wings to minimize drag.

If this refers to the "insect-net" idea, I agree it is nonsense.  Of course
some birds do use their wings in foraging (eg the Black Heron).  Again, I fail
to see what this has to do with the idea of an upward leap from a standing
(rather than a running) position accompanied by a flutter (as in grouse or
cranes, for example).

  Second, and more important, neither 
>model addresses the question of *why* the wings should be flapped, and 
>how imprecise forms of wing waving needed for predation or stability 
>developed into true flapping...

I have not done this, of course, but I have suggested here that any extension
of a leap, or slowing of a fall back, could be of use in getting at prey
slightly out of reach of "mere" leapers, or in making a display leap more
striking.  Thus even a slight development in that direction could be
selectively advantageous.

 >yet the first "flights" of a fluttering proto-flapper would have been at 
>low speeds, where the energetic demands of flight are at their most 
>extreme (Clark 1977), and the wingbeat cycle is at its most complex 
>(Rayner 1988a,b).  This model need not be considered further."

This again assumes that the function of proto-flapping was to get from point A
to point B.  This need not have been the case; many flycatching birds
return to
their original perch after an aerial foray, and displaying leapers are only
trying to show off, not to get anywhere.  Under such circumstances I don't
think much in the way of aerodynamic stability need to have been involved.

This is why he 
>supported the hypothesis that flight in birds evolved when theropods ran 
>and jumped into the wind.  This fails because it assumes that wind would 
>be constant and that early birds did not the have the special anatomical 
>controls that modern birds had.


Again - this is NOT what I am suggesting (and bear in mind I am not
claiming to
be any more than an armchair quarterback here!)

--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@inforamp.net