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Re: Secondary Flightlessness



At 01:46 PM 8/3/98 -0400, larryf@capital.net wrote:
>I can see no problem with secondary flightlessness
>occurring....many times.

Nor can I.  One thing that seems to be ignored in all this discussion is
that neither I, nor Brochu, nor Troutman, nor Wagner, nor Hopp, nor etc. (as
far as I can tell) say that it is an impossibility, or in fact an
improbability.  It is indeed regarded as a potential.

However, we have offered suggestions that, methodologically, we do not yet
have evidence to prefer this scenario over other ones (at this time) and
indeed methodological reasons to (currently) prefer another scenario over
this one.

>If one looks at the energy requirements necessary
>for birds to retain their properties of a flying existance, it`s easy to see
>why they would take any opportunistically available route to a cursorial
>lifestyle.

Actually, unless there has been some post-1990 publishing on this subject,
this is not necessarily true.  Rick Vasquez (whose actual dissertation topic
was recently discussed here) wanted originally to work on this problem: to
see if flightless birds really DO use less energy than their flying
counterparts.  Although we are all familiar with this scenario, it turned
out that (according to his library research) no one had actually
demonstrated that (for instance) flightless rails or flightless ducks have
lower metabolic rates than their volant sister taxa.  Unfortunately (for
this project, at least), we didn't have the appropriate facilities at Yale
at that time, so Rick moved on to bird wrist anatomy.

Maybe Orenstein or someone else who knows more about neornithology than I
might know if anyone has demonstrated that flightless birds really are
slower metabolically than their flying kin.

(Okay, I can think of a few taxa (kiwis, for instance) who seem to be slow
and sluggish relative to flying birds, but are their sister taxa among the
ratites of similar metabolism?  If not, then this wouldn't be evidence for
reduced metabolism during the origin and development of flightlessness, but
instead one of kiwis (many) unique features.)

(Maybe the kakapo (sp?  big flightless parrot) might be a good test subject
for this?)

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661