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Re: Argentavis feeding habits

Jonathon Schmidt <ashmidt@flash.net> wrote:
> Is it known what Argentavis likely fed on?   Was it a predator or a
> scavenger like it modern relatives(the condors) .  I soppose looking at
> design of it's feet( if its feet have been found) would help answer the
> question.

According to Terra Volume 31, Number 1, Fall 1992, specifically the article
"The Teratorns" by Kenneth E. Campbell:

"Because these birds (teratorns) have no living relatives, we can only know
about them from studies of their bones."

In this case, I believe that the author was using the phrase "no living
relatives" to mean "no living descendants," as the teratorns were surely
"related" to modern birds, albeit not so "closely."

As the article demonstrates, the skull of _Teratornis merriami_ does not
closely resemble that of the California Condor.  The initial conception of
the teratorns as scavengers is based on a comparison of the leg bones in
these two groups (teratorns and condors), and has led to the classic
depiction of the tar pits attended by oversize condors, an image that
prevailed for over 70 years.  The teratorn's large, hooked beak and jaw
architecture are likened to the features of active predators which capture
small, live prey.  The heavy body and short legs suggest a stalking (as
opposed to a running) strategy.  They would have swallowed their prey
whole.  Campbell proposes that the La Brea teratorns may have preyed upon
the young chicks of the extinct California Turkey.  As opportunistic
scavengers, teratorns would have been limited to scavenging small animals.

Wing and hindlimb morphology suggest a condor-like wing shape and flying
style.  Their large size and large wingspan suggest that they would have
been limited to open countryside.  Campbell believes that teratorns would
have had feathered heads which may have been light in color (all the better
to blend with the sky, my dear).  

Not exactly the 1925 Charles Knight image, is it?  The cited magazine shows
the La Brea teratorn (among other creatures) on the cover in a detail from
Mark Hallett's epic 1988 mural, "Treasures of the Tar Pits."  Hallett
doesn't give the bird a light-colored head, but does show it stalking
turkey chicks on the ground (the big bully).  Knight was a visionary, but
he was understandably limited by the prevailing paleontological views of
his day.

Hope this helps.

-- Ralph Miller III     gbabcock@best.com