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Re: large fossil birds
--- jrc <firstname.lastname@example.org> wrote:
> ----- Original Message -----
> From: "don ohmes" <email@example.com>
> To: <firstname.lastname@example.org>
> Cc: <email@example.com>
> Sent: Thursday, December 01, 2005 8:12 AM
> Subject: Re: large fossil birds
> > +++++++++++++++++++++++++++++++++++++++++++++++++
> > In wild type D. melanogaster (and drosophila
> > generally), AR increases with size. Even a small
> > sample of males ranging .5-.95mg will conform to
> > trend (p <.05), and given controlled conditions,
> > increase can be consistently (75-80%) measured
> > flies with a weight differential of .1 mg! (Don
> > unpublished data). In insects, the correlation
> > to hold across taxa, _within wing (and presumably
> > flight) styles_.
> This is a Reynold's number effect.
> > This implies that the optimal AR within
> > generally scales w/ size,
> > and also that the AR at
> > which tip slots become unfavorable in falcon-sized
> > birds is lower than in pelican-sized birds.
> I'd have to spend a few minutes thinking about this
> one. It's a function of
> the relationship between weight, speed, aspect ratio
> and profile drag. At
> first blush, I'd say its very likely true. It is
> also a function of the
> birds' line of ancestry, and random genetic
> variation and not entirely
> related to aerodynamics.
I'm of the "optimizer" persuasion; but maybe birds
have more morphical slop than flies... actually they
do, but I think it is still limited.
IMO-- Small diptera usually have near zero slop. In
insects, flightstyle determines optimal morphology;
within "high performance" flightstyles, ancestry can
be largely irrelevant.
> > It also (probably) explains why tip-slots
> disappear entirely
> > (IIRC) in smaller birds.
> May well do.
> > As previously mentioned
> > (again w/ the IIRC), comparisons between volants
> > different sizes is basically iffy.
> If Reynolds number effects are taken into account,
> I'm not sure I'd agree
> with this. I do recognise that there are
> substantial limits on comparisons
> between extreme differences in size.
I assume you mean mathematically. M. Dickinson is the
only one I know of that accounts for Re
experimentally, although I am not current; is there
even a working variable-pressure wind tunnel around
> > Does anyone happen to know what the smallest bird
> > tip-slots is?
> Good question. I don't know.
Drat. Hoped you might know.