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Re: Cost in Aquatic Birds



David Marjanovic (david.marjanovic@gmx.at) wrote:

<There are also excellent arguments against both. (Still waiting for the
paper on vertical running...)>

  The arguments against are often the opposite of the arguments for ...
the two theories use positive data both, and little negative data, do more
of a job to prove, than disprove, that makes it difficult to argue for any
one theory. It is not enough to build up your theory, you must also try to
take it down. Not that I think you've done anything like I will suggest,
but you've done a good job of championing Ebel, but have not truly tried
to tear his theory apart.

<Again I don't think Archie could qualify as aquatic. Just as semiaquatic
as a dipper.>

  Dippers are not semi-aquatic, as they feature no adaptation to a life in
the water. More on this below...

<I don't think I need to care what truly-aquatic birds have :-)>

  It does if you are trying to support a theory on *Archaeopteryx* using
wing-propelled swimming to evaluate evolution of flight ... one must
ascertain the capability of the skeleton to swimming ... one looks at
extant analogues of swimming animals, and compare. In the instance that an
animal does not compare to anything we know, we can provide suggestion for
a unique concept of that animal, a paradigm if you will.

<(sterna is already the plural, of sternum)>

  I think that all three are used. Both sterna and sternum are stems from
sterno (something broad) in Latin. Sterna, if a noun, if feminine, and
becomes sternae ... whereas sternum, pluralized sterna as well, is a noun
constructed for specific anatomyical usage. Maybe the linguists can help,
I think this was also discussed on the list some time ago ... I was being
loose with the terminology, and have used both sterna and sternae
interchangeably recently....

<Pat Shipman: Taking Wing sez the keel "only" serves to keep the air sacs
between the muscles from collapsing, which allows the heat to be
transported away efficiently; the absence of a kee> would just mean the
inability to _sustain_ flight for long periods of time.>

  This may not be exactly the truth, though it is part of it. Increase in
keel size is coincident with an increase in the insertion of the m.
pectoralis position. Birds with a larger lateral keel surface area are
better fliers, including aquatic fliers. This has not been exactly
quantified (unless I missed a ref), so take it with a little pinch of
salt, but increase in pectoral attachement is corrolary in the evolution
of birds (Chiappe, 1996, 1997) with specialized flight ability. This
indicates a link between keel size and flight performance. Now we _did_ go
through this on the list. There _is_ cineradiographic and osteological
analysis of this subject published. Give me a few days and I can dig up
the refs. Dial has done work on this subject, as has Yalden.

<Same for the dipper (except its nostrils) AFAIK.>

  A lot of birds have the ability to seal their nostrils. The thing is,
all dipper aquatic behavior is just that: behavior. And that does not
fossilize. This is part of Ebel's theory's flaw: the dipper has no real
features except sustenance of breath to permit it to swim into deep water
and take prey.

<...which is a foot-propelled diver.>

  Mostly. Cormorants also use their wings as aerofoils (I've seen them
dive, though not in person) as part of the upsurge from a dive. They use
this to increase their surfacing speed.

<I am aware that many arguments for FUCHSIA are negative. :-)>

  I see flaws, and I report. That's part of the scientific process. It
permits refinement, or rejection.

<Do they actually dive? AFAIK only their feet touch the water if the fish
isn't so strong that it can drag the osprey down.>

  I don't know how many times I've seen osprey dive. They plunge at an
angle into the water, grasping with the feet, if the object is too deep to
snatch from the surface, and use their wings to propel them to the
surface. Actually, ospreys will use the force of their own entrance to
create a rebound which they use to ride to the surface without slogging
their wings too much for flight. Ospreys spend a lot of time oiling their
feathers before diving because of this, and need to find a perch close to
their catch to preen before they can feed properly.

<It does have the unserrated teeth of a fish-eater, though.>

  Fish-eaters typically need _lots_ of interlocking teeth ... avian
fish-eaters, though, lack 'em, so it's not required. As for the lack of
serrations, there are lot's of basal birds and maniraptoran theropods with
non-serrate teeth, so this is evolutionary first, ecological secondarily
if at all.

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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