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



--- On Wed, 9/24/08, Mike Habib <habib@jhmi.edu> wrote:
> Ah, and it returns.  This came up in another recent
> discussion, which sadly became rather more heated than it ought to have
> been.
> In any case, I suggest being careful with the term "easy" in this 
> context. It does, indeed, take less power to drop from a height
> (assuming you are already there), than to leap from a substrate.
> However, what is "easy" in terms of biological systems depends
> entirely on the ancestral state.  Birds inherited highly powerful
> hindlimbs from their ancestors, which were mechanically capable of
> powering leaping launches.  This doesn't mean that the origin of flight
> in birds was purely cursorial in nature, but it does indicate that an
> arboreal stage isn't mechanically required.

On the subject of leaping launches, here is an excellent slow mo video of a 
seagul doing so (among other things)
http://uk.youtube.com/watch?v=gAtIIlEVTok&eurl=http://people.eku.edu/ritchisong/554notes3.html

I'll note that the leap coincides with a wing beat, and is into the wind.
Not all birds will leap into the air, quite a few take running starts, or will 
do so if they do not have the aid of wind.
A hummingbird need not leap or run, the wing beat alone is powerful enough.

When discussing current "leap launching" birds which have very well developed 
flight muscles and strokes, I think it might be an error to attribute the leap 
launch ability to birds inheriting highly powerful hindlimbs from their 
ancestors.

A primarily cursorial bird like a wild turkey probably has hindlimbs more akin 
to the ancestral coelosaur than a seagul, the turkey's legs certainly have 
proportionally more muscle mass than those of a seagul - yet its launch style 
is most often (personal observation, not neccesarily factual) a running launch.

I would suggest a no wind leaping launch on flat ground is technically more 
demanding (from an engineering point of view) than a running one, and requires 
a well developed flapping mechanism, or very well developed leaping mechanism 
to work.
A running start just requires clearance for the wings, which need to have 
sufficient efficiency and surface area to have a stall speed lower than the 
animals top running speed. Then even weak flapping should be sufficient.

But of course, the ancestral condition is a large factor.
Something like a frog which already is highly adapted for leaping, and poorly 
adapted for running, would be much more likely to evolve flight(it would be 
"easier") by leaping than running.

Lacking well developed flight muscles, in my opinion, an exceptional leaping 
aparatus is needed, but only a mediocre running aparatus.

But this is getting off topic, (to an old one)