[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: The origin of flight: from the water up
> If you have many mouths to feed, you better be a good
> swimmer to catch the food necessary to ensure the
> survival of all the chicks. Otherwise, you'd be
> wasting energy on long wings and more eggs than you
> can take care of. In other words, why have long wings
> for brooding if they make it difficult to feed your
> progeny? If anything, evolution will favor a smaller
> brood or egg size and smaller wings.
Good argument. However, for a bird, Archie's wings are pretty short. That's
certainly the plesiomorphy and therefore rather negative evidence, but it
isn't evidence against.
> > When the theropods specialize in this behavior
> > instead of staying more generalistic... like a
> > dipper. AFAIK dippers are as extremely pneumatized
> > as any passerine, and much more than a basal
> > coelurosaur.
> They also have to grip the river bed
Archie wasn't so extremely pneumatic, and dippers still do fly around
> and can only stay
> under for 30 seconds.
> In the web pages I've visited
> looking for more information on this bird, it says
> they have stubby wings - just what I'd expect.
Sure? Even stubbier than Archie's?
> It probably isn't as good a flier as other small
> songbirds, as a result.
I'll bet quite something that Archie was a considerably worse flier than any
> It's also pretty telling that
> birds like brown pelicans have to plunge-dive from 60
> feet above the surface.
Why is that telling? Pelicans are big and specialized. Many smaller birds
> > I don't know anymore whether I've seen that on TV,
> > but Feduccia mentions many species of auks and
> > petrels that fly straightly through waves. Haven't
> > seen lots of dippers on TV.
> Maybe they simply fold up their wings and shoot
> through them.
Feduccia says explicitely that they flap in the waves. And I've seen several
seabirds (gulls?) fly underwater on TV.
> _Microraptor_, while it's halluces may not be
> reversed, could have climbed trees.
Apart from the effects of its size, it must have been a much worse climber
than I... or than a rat, to get closer to its size.
> IIRC HP Mickey
> Mortimer said new specimens show a reversed hallux?
> May just be wishful thinking :)
On the published photos, the hallux isn't longer than Archie's, seems to
originate at the same height above the other toes as in Archie, and is
disarticulated from the metatarsus, so just how reversed it was can't be
told. The latter also holds for *Caudipteryx*... and *Archaeopteryx* itself.
> > > And with very little mental work I can see them
> > > transitioning from gliding to powered flying.
> > from gliding to flying [...] that transition
> > is probably impossible, as flapping destabilizes a
> > glider (screws up its angle of attack and all
> > that). No living glider flaps.
> If flapping only destabilizes a glider, then why do
> birds flap, glide for a distance, then flap again?
> Wouldn't that cause problems for them? And yet many
> birds of prey do this. [...] Call it the "undulatory
> origin of powered flight" if you will.
Chatterjee has proposed the same... I think undulatory flight can only arise
in a fully capable flapper, it just looks too difficult for me. :-) And in
the non-flapping phases songbirds at least don't glide, they simply tuck in
their wings and fall.
> > > After a short bout of gliding, they would
> > > allow the lift generated to push the wings back to
> > > vertical.
> > And then they fall again. Counterproductive.
> Not counterproductive at all. It generates velocity.
Well, do this 2 or 3 times, and you end up 20 m below the spot you wanted to
> What was it supporting or gripping? I'm not sure, but
> I'm willing to venture a guess. Only if the
> metatarsals were held flat against a tree trunk or
> other surface would the halluces be subjected to
> evolutionary pressures.
Possible. But maybe just prey was held against the ground. I'd still expect
longer halluces inserting farther down for this purpose.
> Let's say your FUCHSIA model
> is correct for a moment. How would an opposable hallux
> evolve and then migrate down to the same plane as the
> other phalanges in the foot?
This is outside the realm of FUCHSIA. =8-) I think arboreality came later,
after flapping flight on the level of *Confuciusornis* and/or *Sapeornis*
> Birds simply flew out of
> the water, landed on a perch, and by a macromutation
> miracle modified this appendage?
Erm... yes, basically, but that took some Ma... :-)
> I'm also interested
> in what you think _Rahonavis_ was using its giant
> ungual for. Disemboweling fish?
I think *Rahonavis*, with its very long wings and legs, had specialized into
a secretary bird analogue that, unlike a secretary bird, didn't need to kill
its prey with its jaws.