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Tails and Wind Tunnel Studies - Re: Longer Tails in Birds: Functional "Re"Evolution



On Thu, 14 Feb 2002, Jaime A. Headden wrote:
> Mickey Mortimer (mickey_mortimer11@msn.com) wrote:
> 
> <<It's less derived than Sapeornis based on- cervical centra not
> heterocoelous; absence of pygostyle?.>>
> 
> David Marjanovic (david.marjanovic@gmx.at) wrote:
> 
> <_Long tail_. And I'd need good evidence to accept a reversal of that,
> given the fact that all other known cursorial birds have never reevolved a
> sizable tail, even though they could use it.>
> 
>   Actually, birds have redeveloped the long tail. It's just formed from
> feathers rather than flesh and bone. There would be no need to attempt
> some paedomorphic development of the more complete tail when readily
> adaptible structure (feathers) are available, and take less energy to
> modify. This is why [I think] that birds never re-adapted the bony tail.
> It may be no more a simple question than that. Of course, one needs to
> observe birds using this in such a manner as would a bipedal lizard in the
> same instance ... and voila! we have such cases around us. True, in
> hypercursoprial birds like ostriches, there is a very short tail, but this
> is true in hypercursorial theropods, too ... reduction of the tail and
> elevation of the neck resulting in narrowing the turn radius and allow
> greater turning control. Nonetheless, comm ents please?

The recent posts on tails reminded me of a short article in the 7/14/01
Science News.The article related results from two journal articles
involving wind tunnel tests on bird tails (refs at bottom).

The Science News article mentions the debate over the shape of a bird's
tail and whether its shape (noted as being often a delta-wing shape) is
dependent upon aerodynamics or for sexual attraction. Apparently these are
the first wind tunnel tests of assumptions about the tail shape.

A tail without a body has lift effects but not quite so with a body attached. As
the tail spreads lift is supposed to increase according to theory, but it 
didn't.

What they also found was that a folded tail decreases drag by 1/4 to 1/2. One
of the researchers speculates that tails offer tradeoffs among flight styles.

"Streamers ...added to bank martins cut their performance on straight flight
but improved maneuverability."

Ok, now with all that in mind, I'm curious if any wind tunnel studies of 
paleo birds has been attempted. (Yes, approximations and guesses will be
needed to form a model but I would think it's doable.) The comment about the
streamer on the martin aiding maneuverability makes me wonder if some
deduction can be made about the flying styles of these paleo birds.


 Maybury, W.J., J.M.V. Rayner, and L.B. Couldrick. 2001. Lift generation
 by the avian tail. Proceedings of the Royal Society of London B 268(July
 22):1443.

 Maybury, W.J., and J.M.V. Rayner. 2001. The avian tail reduces body
 parasite drag by controlling flow separation and vortex shedding.
 Proceedings of the Royal Society of London B 268(July 7):1405.