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Re: energy-effective?



I know all bones are elastic to some degree, but wonder if 'flight'
calls for a particular range of elasticity. 
I wonder if different species of birds have differing elasticities of
the bones.

When I find a dead passerine, the bones seem more brittle than the same
bones on a seagull.
This COULD just be cause the seagull is found in an intensely more humid
environment than a dead robin or a dead bluejay usually is, but I'm
wondering if birds (or dinosaurs) of arid regions such as roadrunners or
some vultures and buzzards would be nutritionally or hydratingly
disadvantaged in the making of the elastic bone property.  I know BATS,
if not fed properly, can develop rickets and other degenerate bone and
tissue deseases that can cripple them from flight.  Bats are commonly
found throughout most environments except very high altitude moutainous
regions, tundra, out at high sea, and pretty much anywhere else they
won't find food. Dinosaurs can be found in pretty much the same
environments, with the possible exception of tundra.

Would this elasticity be controlled more through diet, or more through
genetics?  

-Betty


"James R. Cunningham" wrote:

> Yes to the latter, if you replace the word 'tension' with 'stress and strain' 
> and the word
> 'bone' with 'bone/tendon/ligament complex'.  The advantage to the animal is 
> that it allows
> the timing of the energy transferred to the atmosphere to be adjusted, and 
> that it reduces
> the peak forces involved in the flight stroke. It allows the animal to spread 
> the muscle work
> over a longer time period, reducing peak loads, and allows the animal to fly 
> with a slightly
> smaller muscle mass than would otherwise be required.
> 
> > Maybe the answers are
> > somewhere in the text (than I'm sorry I've missed it/didn't
> > understand it) or in the chapters yet to come.
> 
> I haven't read the book yet.  Do you recommend it?
> 
> > It this kind of flexibility normal in bones from birds? Is this a
> > characteristic which leaves evidence in fossils; what I mean is this:
> > can one looking at the bones of a archaeopteryx see that the bones
> > were flexible in life and how?
> 
> It is possible to tell this in pterosaurs (in some circumstances, and in a 
> limited way).  I
> would expect the same in birds, but have not investigated that in any way.  
> Ken Dial has done
> strain gage work on the humerus of flying pigeons that might address your 
> question.
> 
> > I just thought about it this weekend and 'build' a very experimental 
> > recoiling cage
> > with sticks and elastic material and it seemed to be very easy to keep the 
> > movement
> > going once it had started (equivalent for a prolonged flight). For only a 
> > few 'flaps' (or
> > the equivalent of a short flight) it seemed a bit more difficult (and thus 
> > less
> > energy-effective) to me.
> 
> I think you may well be right here.  For a short flight, I would expect a 
> bird to use more
> anaerobic muscles, and I would expect him to press a larger fraction of 
> muscle fiber into
> short term use.  I would also expect any elastic energy storage mechanism to 
> have a natural
> resonance frequency.  Since animals commonly beat at a slightly higher 
> frequency on takeoff
> and on landing, I would expect any storage system to function effectively 
> either in cruise or
> on takeoff or landing, but not all three.


-- 
Flying Goat Graphics
http://www.flyinggoat.com
(Society of Vertebrate Paleontology member)
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