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Re: Third claw for climbing was Re: Pro(to)avis



I find it somewhat surprising, but--
One "onramp" (love the term) advantage for
proto-feathers I haven't seen mentioned in print is
camoflage, a fashion accessory particularly useful to
terrestrial ambush predators, the overset for pounce
or perch hunting.

Anybody got a ref?



--- Graydon <oak@uniserve.com> wrote:

> On Sun, Sep 18, 2005 at 07:55:42PM +0200, David
> Marjanovic scripsit:
> > >So there's nothing to say that our purported
> Pouncing Proavis is either
> > >hunting alone *or* directly pouncing on prey.
> > 
> > I should have thought of the first point!
> 
> Those sickle claws -- at least the proportionately
> large ones -- are not
> the armament you'd expect if they're hunting smaller
> prey.  Which in
> turn suggests group hunting behaviours, if they're
> tackling prey their
> own size or larger.
> 
> > >Maybe small family groups are using pouncing to
> get down from lookout
> > >positions all *around* prey, greatly increasing
> their collective
> > >chances of making the capture without trying to
> do the direct,
> > >modern, hawk-pounce on it. [...] Pouncing
> wouldn't even have to be
> > >particularly *close* to prey for that to work; it
> would just have to
> > >provide a modest improvement to the odds of prey
> capture.
> > 
> > Would it really be an improvement over just
> jumping down straight and
> > then running, at least when the cost of the
> feathers etc. is taken
> > into account? 
> 
> Dunno, I haven't tried to quantify the energetics.
> 
> But if you can, frex, safely leap from the rim of a
> 5m high wash instead
> of a 3m high wash, you've expanded the territory you
> can pounce-hunt in
> substantially.  That's got to be worth something.
> 
> If you and Uncle Fred can end up on the _far side_
> of the prospective
> prey, while the three sub-adults wind up on the near
> side, that's worth
> something, too.  (Harris hawks do vertical
> envelopment like that.)
> 
> Also, you're exapting feathers you got for
> insulation, brooding, or
> display, not growing them special; otherwise there's
> no onramp to the
> aerodynamic uses.  So *any* increase in glide range
> or landing precision
> starts to drive the aerodynamic uses of those
> feathers.
> 
> What I'm trying to get at is *not* that 'leap with
> both feet' predation
> isn't a driver for aerodynamic exapation of
> feathers; I think it's clear
> that it is, since landing on anything with both feet
> is hard.
> 
> I'm just trying to point out that there's more to
> the predation activity
> than the get-a-foot-on-it-and-kill-it step, and that
> there are plausible
> ways for the precursors to making the kill to be
> drivers for aerodynamic
> feather adaptation.
>