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Re: Senter 2006, Confuciusornis, and humeral mobility



On Mar 25, 2011, at 5:31 PM, Jason Brougham wrote:

> With a 1.2 meter wingspan  Confuciusornis should be able to engage in steady 
> flight with a stroke angle of just 56 degrees, right? 25 degrees above the 
> horizontal and 31 degrees below should do fine. Those are the exact observed 
> numbers for Milvus migrans, the Black Kite. Those numbers are from the 
> supplementary data table from the Nudds et al. 2004 paper on Strouhal Numbers.
> 
> What mass are you using, Michael?

I ran a range from 150-180 grams.  Keep in mind that the stroke amplitude does 
not vary only with span loading, however, so birds with similar spans and 
masses can have different prerequisite flapping gaits (though they'll be close, 
as those are two of the primary variables).  I actually have the raw Strouhal 
data so I was able to check that as well, good call.  The kite is expected to 
have a somewhat smaller stroke amplitude than Confuciusornis, based on what I 
have, but then I'm not absolutely certain about the wing area and body mass I'm 
using, either.  Nonetheless, that 25 degrees above the horizontal does make a 
fair bit of difference.  This is why I was quite specific that I was assuming 
*no* abduction above the horizontal.  The main problem, however, continues to 
be the climb out issue.  The steady flight stroke angles are not applicable to 
phases of sharply accelerating flight, especially when climbing after launch. 
There could be a solution to that issue for Confuciusornis, but I don't see it 
at the moment.  I am dead-set that Confuciusornis could not have been a powered 
flyer, only that it is problematic to reconstruct it as so if one assumes, full 
stop, that it had no supradorsal abduction.

Cheers,

--Mike


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181