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



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.