RE: Bambiraptor complete!

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Ronald Orenstein wrote:

> >If modern birds are prepared to strike each other using their wings
> >(and some species even have metacarpal spurs expressly for this
purpose),
> >and risk damage to the remiges, then I don't see why predatory
> >"dinobirds" would have hesitated at using their forelimbs for prey
capture.

>I do not think these are really corresponding situations.  Birds that
>use their wing spurs in interspecific combat, are, first of all, using
>them much more rarely than a predator depending on its forearms would do
>(as actual fights are less common than bluffs), and, second, the nature >of
the stroke is quite different.  

Very true.  But if the protobird doesn't use its wings for powered flight,
but simply for gliding or parachuting (for example), then a few battered,
gore-stained or missing feathers may not be that important.  However, once
we reach the stage of a powered flyer, in which aerodynamic performance is
the overriding concern, then the bird would probably want to prevent its
wings from getting entangled in predatory engagements.  (Unless it's
flightless - as proposed for _Titanis_.)


>The risk to the remiges of a bird or
>protobird trying to use a fully feathered wing to subdue a struggling >and
bleeding prey animal still strikes me as high.

It might depend on how big the prey was.  That's one of the intuitive
attractions of an insect-catching protobird - insects aren't that big, and
bug guts wouldn't foul the wing that much.  If the jaws alone are used to
snatch insect prey, then there's no risk at all.

The notion that the forelimbs of birds or protobirds could serve as both a
prey-catching instrument and a wing is discussed by Alan Gishlick in the
Ostrom Symposium volume (_Origin and Early Evolution of Birds_).  Based on
the anatomy of _Deinonychus_'s forelimb, he doesn't believe these functions
are incompatible.  Gishlick even suggests that _Deinonychus_ might have had
feathers attached to its middle finger.  

By the way, Gishlick's essay on hand motion in _Deinonychus_, complete with
superb illustrations (including the "predatory stroke" from four different
angles), is one of many brilliant articles in the Ostrom volume.  Great
work!



Tim