Re: flight stroke (pretty short)

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

----- Original Message -----
From: "Waylon Rowley" <whte_rbt_obj@yahoo.com>
Sent: Wednesday, May 08, 2002 9:33 AM

> > Does flapping keep the effective surface area the
> > same? ~:-|
>
> Doesn't that depend on the time interval between wing
> beats?

Probably. :-]

> > Does any living glider do that?
>
> Living gliders can only provide so much information on
> the evolution of flight, especially considering the
> variations of this strategy in the dissimilar groups
> that practice it.

Especially because there are so many groups that practice diverse variants
of gliding do I think that it's likely to tell something if any of them does
or does not show a certain behavior.

> Wouldn't incipient flappers be
> quickly out-competed by more derived flappers?

Hm... I think this implies that gliders would just as quickly be outcompeted
by incipient flappers.

> > FUCHSIA --
> > the theropods flapped faster and faster and
> > realized afterwards that they had left the water;
>
> - Which would come as a great shock, and probably
> cause the bird to tumble back into the water. The
> sudden transition would be confusing, disorienting,
> and destabilizing.

Might still provide a selectionary advantage if it tumbled back far enough
away :-)

> > vertical running -- they kept on running after the >
> tree had ended. :-)
>
> I like the idea of vertical running, but I'd propose
> that whatever they were running after (say a young
> pterosaur?) leapt off the trunk and they simply
> pursued it. Wouldn't  branches stop the progression up
> the tree before it reached the top, too?

Okay, I was oversimplifying :-)

> > There are still 2 genera or so of long-tailed bats,

Don't know how I arrived at 2 genera... I mean the 4 species of
Rhinopomatidae.

> > and I wonder why pterosaurs evolved short tails so >
> > late (but twice).
>
> So, you deny that there is a phenomenon here?

I don't.

> There must be some advantage to having a short tail or
> some disadvantage to having a long tail.

I just wonder what exactly the disadvantage of a long tail is. -- That of
Rhinopomatidae is very thin, so I think it doesn't contribute much to
aerodynamics and the position of the center of gravity. The book doesn't
mention at all what such a tail is good for. ~:-|

> > Requires very, very long femora. We have such long
> > ones, *Yandangornis* had, but I can't think of
> > others...
>
> Eh? Sorry....don't follow you.

Sorry, depends on how close the elbows are held at the body. I mean long
femora that could reach the shoulders to seal the entire gap.

> > Sounds possible (indeed the humerus never points
> > directly laterally in birds), but wouldn't longer
> > feathers evolve more probably?
>
> Behavior evolves faster than feathers, or it's just
> learned. Holding the humerus against the trunk is a
> faster fix than growing longer feathers.

But if we start from a glider that's just starting to evolve wings... never
mind :-)