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Re: Phylogeny of Maniraptora



Graydon wrote:

> not a good example of getting energy from a headwind as such.

Possibly not, since a headwind as such cannot supply energy to a flying
deviced submerged in the uniformly flowing medium.
> I was thinking of flying squirrels, which are probably gliders by your
> definitions given, but which (so far as I know) cannot wind up higher
> than they started even with perfect conditions.

Actually they can, at any time when they are airborne in an updraft
greater than their sink rate.  Not that any sensible flying squirrel
would have any urge to do that.

> > I'll drink to that. Though I've noticed that albatrosses don't always
> > get it right upon landing and sometimes go fanny over teakettle.
> 
> I've seen a few gulls doing non-flapping water landings do that, too.

I've done it myself a few times, in airplanes. Embarrasing.

> What I was mostly thinking of, though, was domestic chickens, which
> can't really fly, but which expend immense amounts of energy on attitude 
> control if you push them off the ridge line of the building they're sitting 
> on instead of nabbing them and stuffing them in a sack.

If they can't fly, then how come some of the running chickens that I
used to chase (when a kid, as a prelude to Sunday dinner -- catching the
little suckers was my job, but I was a sissy and Granny did the deal
with twisting their necks) wound up about 20 or 30 feet up in a tree? 
Those chickens lived to run another day.

> (Good flyers, no; good escape artists, yes.)

They weren't great flyers, but they were better than me at it.  And they
could gain altitude while doing it too.
> 

> seen an ostrich really run.  Her wings were moving in small flapping
> motions; I don't think the two sets of limbs are completely decoupled
> unless something comes along to provide pressure *to* decouple them.

That latter may well be true; I don't know.  But I do know that when
running, they will use the wings appropriately to help them turn.
> 
> > > The trick is 

> That's running up the slope/tree trunk using wing assist to maintain
> traction and climb steeper slopes;

That's not a trick; that's just plain old physics.

> and it provides a way for
> small variations in slope climbing ability to be subject to strong
> selection pressure -- use a predator escape -- so there's a ramp for
> going from predatory-stroke-plus-feathers to
> arm-motion-optimized-for-aerodynamic-forces.

I agree. Though to be fair, I think there were probably a lot of other
things going on at the same time.

> > Doesn't that sort of depend upon the duration of the anticipated
> > flight?
> 
> I was thinking that it would depend on the peak stress as you launched
> yourself up, into the air.

Likely, and launch stresses may not have the same alignments as the peak
stresses incurred during flight.  For example, in Quetzalcoatlus the
most robust skeletal bracing isn't aligned with flight loads -- it does
appear to be aligned with launch loads.
> 

> I'd say that if you can go from point A to point B, where point B is ten or 
> more times your head-to-foot height above point A, under your own
> power and in the air, you're a flyer.

OK. That gives me a good visual image of the energy involved by your
definition.  Thanks for the clarifcation.  Those childhood chickens were
flyers for sure.

> I think with what we know now, feathers and flapping are a given; it's
> ability to grab onto the air and climb that provides evidence of powered 
> flight.

I think we have a distinctly different mental image of what constitutes
powered flight. Which is OK by me.