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Re: Senter 2006, Confuciusornis, and humeral mobility



What besides span and loading determines the stroke angle?



>
> 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
>
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544
jaseb@amnh.org