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Cost in Aquatic Birds



The origin of flight in birds is tricky because there are several lines of
evidence that need to be considered: morphological, ecological,
biophysical, and the fossil record itself. Though recently the origin of
flight has involved trees, either in that flight came down, or went up the
tree, the origin of flight need not neccessarily involve flight in any
way, shape or form. Problematically, solutions to biophysical constraints
as performed in aerodynamic and morphological studies involve primarily
the trees. Recent investigations into "vertical running" have given
credence to the grounds-up theory, whereas the dromaeosaurs of the Jehol
biota has given credence to the trees-down theory. There are excellent
arguments for both.

  Problematic to these is the idea that for some reason, *Archaeopteryx*
pectoral anatomy was insufficient for sustained flight, much less powered
flight, and proponents of this include Ebel who proposed an aquatic-thrust
capability for *Archaeopteryx* to somehow _perfect_ the  thrust generator
of the wing for flight. Problematically, there are several morphological
features in aquatic birds that *Archaeopteryx* does not have. Foremost
among these is the elongate wings and short feet. In all quatic birds that
are wing-assisted swimmers, especially penguins, the wings are very
robust, but very short, the pes anisodactyle and webbed. Nearly all
aquatic bird feet are either lobed (grebes and loons) or webbed
(pelecaniforms, anseriforms, sphenisciforms and procellariiforms). Tissue
preservation in *Archaeopteryx* is not perfect, but it would appear that
the non-anisodactyle (heterodactyle) pes does not support webbing and
studies by Yalden support these were in fact arboreally suited, were not
tailed but strongly clawed. No truly-aquatic bird possesses such feet.
Even wing-powered swimmers have large sternae, and in fact the larges
sternae and keels in birds belong to the purely aquatic *Pinguinus* (great
auk) and Sphenisciforms, and elongate sternae in loons, grebes,
hesperornithiformes, and the great auk and penguins. This is missing in
*Archaeopteryx* (and in fact, only one preserved sterna is known for seven
specimens) and it is quite small and only incipiently keeled.

  Nothing specifically qualifies *Archaeopteryx* for swimming in any way,
shape or form. Ebel supported *Archaeopteryx* swimming nearly entirely
based on insignificant flight musculature and the inability to fly from
small island to small isalnd and still account for the wide-spread
distribution of the specimens in the Solnhofen Limestone. Perhaps an
analogue would be the flightless cormorant.... However, these are not
truly advantageous facts to supporting any lifestyle, and the quality of
the material prevents a cohesive analysis of the fact that *Archaeopteryx*
possessed robust pectoral musculature ... or marginal ones. Knowledge of
the environment is insifficient to support small little islands spaced
well-apart, and these flaws mar Ebel's work.

  Aquatic birds spend a good deal of time in the water, adapting to their
environment in more ways than osteologically, but also in their diet and
integument. For birds to specialize in water, they must make several
sacrifices not afforded in more volant birds. One of these is an improved
flight apparatus, tail size, and integumentary anatomy, including the
extra-integumental feathers. There are few birds that take to the water
easily and still maintain a non-aquatic life-style. Ospreys are an example
of a bird that takes hours cleaning and preparing its feathers before a
fishing dive, and this bird specializes in fish, though it still takes
other prey. Other bird species that are adapted to water are much more
severely adapted, including anhingas, dippers, etc., which still ratain
the ability to fly, but have acheived behavioral or anatomical adaptations
to their prey-involved environment. Birds take a cost to become acquatic,
and this cost is usually in time, time which birds which seek volant prey,
plants, or terrestrial prey use to hunt or eat. Time spent swimming around
to produce flight-capable limbs is not ecologically sound: the only
purpose birds take to the water is to feed, and this absence of adaptation
in *Archaeopteryx* indicates that it probably did not take to the water.

  *Archaeopteryx* displays absolutely no positive data that suggest it was
in any way aquatic.

=====
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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