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Re: uprightedness (was Re: SICB Report, part 1 (long)]
> John Bois wrote:
> > On Fri, 15 Jan 1999, James R. Cunningham wrote:
> > > Pheasants do
> > > pretty well with a long tail. Archies' tail doesn't appear to me to have
> > > been a handicap in flight -- more of a benefit, I'd say.
> > But a flesh and bone tail is heavier than a tail made of feathers.
> The only thing that really matters here is wing loading (or tail loading as
> case might be). Qualitatively, Archie's doesn't appear to have been all that
> great. In the numbers I quoted the other day, I assumed Archie's tail was
> supporting the weight of his legs, or qualitatively, about 15% of his body
> weight. He would have done just fine while carrying that weight, and could
> carried more
> > >...since Archie probably didn't take off flat-footed from a standing
> > > start like a pigeon does...
> > Being able to take off vertically is an advantage for avoiding predation.
> > It also means birds can spend more time foraging and less time planning a
> > take-off route.
> I agree whole heartedly with the statement above, but still doubt that Archie
> was capable of doing so (no supracoracoideus).
> > >...make me suspect that Archie was a fairly effective flyer, probably a
> > better
> > > fit for his specific flight niche than a pigeon would have been. On the
> > > other hand, I also suspect pigeons fit the pigeon niche better than Archie
> > > would have.
> > This is very difficult to argue. One would have to have a competitive fly
> > off to know for sure. Otherwise it seems to me a better position is:
> > the progressive reduction in tail size indicates a competitive advantage
> > for birds which possessed it. Also, there are doubtless closer analogues
> > to archie than pigeons.
> I think you may be making an implicit assumption here which perhaps isn't
> supported by aerodynamics. What causes the competitive advantage of reduced
> tail size for Archie? In what way does the reduction help him? As an
> I seriously doubt that Archie would have been able to fly with his tail
> amputated, because I don't believe he could have launched in that condition.
> how could loss of his tail have helped him? My point is that there are niches
> which need the tail, other niches that don't. Other birds, filling other
> niches, do quite well without a tail, and can fly with their tail removed.
> obvious that a bird that can fly with zero lift on the tail is generally going
> to have less induced drag in flight, and very likely less profile drag as
> However, Archie may not have been able to take off (or land) without his tail.
> If that's indeed the case, then he needed it desperately. I too agree that
> there must be a number of closer analogues to Archie than a pigeon is, but I
> don't know of any that have been so extensively tested in wind tunnels as
> pigeons. The data I have available on magpies is flawed, so I didn't attempt
> use it. I had the wind tunnel comparisons handy for pigeons, but not for
> more similar birds, partly because my focus is on pterosaur flight rather than
> that of early birds. Incidentally, Qsp and Qn flew quite well with a very
> aerodynamic structure (composed of legs and uropatagium) at their aft end,
> a 'tail' loading ('tail' in the aerodynamic, not biological sense) far greater
> than Archie's.
> Best wishes,
> Jim Cunningham