Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "don ohmes" <d_ohmes@yahoo.com>
Sent: Saturday, September 27, 2008 12:46 PM

> > If the areas between modern trees are literally buzzing
> > with insects, why isn't this niche ripe for exploitation
> > by an incipiently flapping, gliding insect-eater?
>
> Because it is currently filled w/ _highly sophisticated and voracious_ 
> flapping insect-eaters. The phrase "...nothing to eat there" was meant to 
> point out the fact that occupying the "empty morpho-space" of which you 
> speak means competing directly w/ vastly superior creatures for the food 
> in the REAL space your "incipiently flapping, gliding insect-eater" must 
> live in.

But if there are still enough insects left anyway, that doesn't matter. Now, 
how many are enough?

> > As for our ancient batty friend _Onychonycteris_... lack of
> > echolocation might have made aerial hawking difficult at
> > night.  Because _Onychonycteris_ seems to have been
> > insectivorous, it may have obtained insect prey mostly by
> > gleaning.
>
> Sure. And/or accidental collisions while gliding from tree-to-tree, 
> leading to hawking and echo-location.

*Onychonycteris* already had flapping flight and lacked echolocation.

> The space between the trees was presumably under-exploited by 
> insectivorous birds at night. Hence the success of the bats at moving in.

Yes, and apparently it still isn't completely full.

> > > Quite correct. Acquiring prey by gliding simply
> > isn't going to work when birds are around, but commuting
> > is always an open option if you have a job to go to...
> >
> > Again, an apparent contradiction.  If obligatory biped Don
> > Ohmes can encounter flying insect populations in his
> > tree-to-tree excursions (presumably terrestrial) - why are
> > these same hordes of insects beyond the reach of a modern
> > aerial glider?
>
> Competition. Unless you know of an insectiferous arboreal environment that 
> is presently free of bats and birds???

"Free" is not necessary. You use the word "underexploited" above...

> > > Also, the debate IS a dichotomy in the sense that you
> > HAVE to start somewhere. Once the ball is rolling, the
> > dichotomy disappears, but that first step is is a
> > > booger...
> >
> > Yes; but the "first step" is not dictated by
> > relative ease.  Natural selection can only act on what's
> > already available.
>
> Exactly! On the gravity-driven side, you have every animal that can or 
> will leap, fall, or pounce from a high place for natural selection to act 
> upon. On the muscle-driven side, ya got nothing but your imagination and a 
> long list of "ancestral constraints". As any manufacturer can tell you, 
> the availability of feedstock and ease of manufacture all count when 
> assessing the likelihood of success.

"Every animal that can or will leap, fall, or pounce from a high place" may 
_not_ include the ancestors of birds. That's our very point.

> > In other words, it makes no difference if gliding is
> > "easier" than leaping upwards to catch insects, if
> > the former behavior never existed in the ancestors of birds.
>
> I did not realize the the non-existence of gliding behavior in proto-birds 
> had been proven...

Did you overlook the "if" part?

That said, the fact that the tertials of extant birds are not simply 
remiges, but lengthened contour feathers that are not anchored to the 
humerus, and the fact that *Archaeopteryx* apparently lacked tertials 
altogether and thus had a fairly broad gap between wing and body, _does_ 
argue _strongly_ against any kind of gliding phase during the origin of bird 
flight. (And that's ignoring the practically complete lack of climbing 
adaptations in all known animals around that origin.)

> I would also recommend avoiding the poker table, although that might be 
> good advice for everyone in any case. :D

Are you aware that " :-D " means you are laughing? Not smiling, not 
grinning, but laughing?