[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Senter 2006, Confuciusornis, and humeral mobility



On Mar 24, 2011, at 6:36 PM, Jason Brougham wrote:

> Takeoff is perhaps a moot point. If, as you say, Confuciusornis was 33 
> percent underpowered even for steady flight then of course it could not have 
> taken off at all, since takeoff requires several times more power than steady 
> flight.

Well, specifically the *climb out* requires more power.  The launch does, too, 
but the power doesn't come from the wings for launch so the takeoff, 
specifically, is not actually a problem.

> However, I found a  case that may be an exception your results about steady 
> flight requiring humeral elevation above the horizontal. According to 
> Pennycuick, in The Flight of Petrels and Albatrosses, 1982, page 82, the 
> species that he observed and that K. D. Scholey filmed had very limited wing 
> motion above the horizontal, with 25 degrees apparently being abnormally 
> high. I am continuing to research those flying vertebrates with the least 
> suprahorizontal wingbeat amplitude, and I will report back.

Indeed; if you want to research species with the least suprahorizontal wingbeat 
amplitude then go right to those species with the longest wings - flapping 
amplitude scales inversely with span.  It also scales inversely with body mass 
at the species level, though within a given animal the amplitude increases as 
mass increases (say, as it adds fat reserves).  Colin Pennycuick talks about 
this in both his older text from the late 70s and his new book (2008), Modeling 
the Flying Bird.  The trick is that those animals are in cruising flight, and 
are fast-flying, soaring-adapted marine taxa with extremely elongate wings.  
They still flap at much greater amplitude and frequency during launch (see Sato 
et al., 2009).  Still, looking for interesting case studies and/or exceptions 
from the living taxa pool is a great idea.  

> Even if the scapulae of Confuciusornis did overhang the glenoids slightly in 
> life, I would bet that a humeral elevation of 25 degrees was still easily 
> possible.

That may be true.  Confuciusornis would need a bit more than that for cruising 
flight, however.  That said, it might even have managed even more.  That's why 
I emphasized that the lack of powered flight pivoted on the Senter analysis 
being exactly correct - if there is even 25% more motion than Senter reports, 
for example, then the picture changes a fair bit.

> Do the equations that you are using to analyze Confuciusornis predict that 
> the smaller albatrosses and petrels can fly without raising their humeri 
> above horizontal?If not, then it is possible that your equations are not 
> adequate to describe the flight of real animals in this special case (those 
> with limited wingbeat amplitudes above horizontal).

Keep in mind that they do raise the humeri above the horizontal, just not much. 
 Furthermore, the hand wing rises and falls more than the humeral excursion 
would tend to imply because the wings are so long (See the Strouhal number 
paper from Nature a few years back).  In any case, yes, the equations I am 
using predict very low amplitudes in procellariiforms - they were developed by 
Pennycuick, who is obviously familiar with such cases.  Good question, though.  
I would recommend looking for taxa with similar span loading to Confuciusornis; 
this will be animals with somewhat stouter wings than albatrosses, but the 
wings are still pretty long in Confuciusornis - perhaps some of the petrels or 
diving ducks?  I suspect mergansers are in the ballpark, though they don't have 
the backswept morphology.  They do have relatively low amplitude flight strokes 
in cruising, though (not as extreme as albatrosses, but it's something).  

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