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Re: large fossil birds


----- Original Message ----- From: "don ohmes" <d_ohmes@yahoo.com>
To: <mhabib5@jhmi.edu>
Cc: <dinosaur@usc.edu>
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 this
trend (p <.05), and given controlled conditions, AR
increase can be consistently (75-80%) measured between
flies with a weight differential of .1 mg! (Don Ohmes,
unpublished data). In insects, the correlation seems
to hold across taxa, _within wing (and presumably
flight) styles_.


This is a Reynold's number effect.


This implies that the optimal AR within flightstyles
generally scales w/ size,


Agreed.

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.

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 of
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.

Does anyone happen to know what the smallest bird w/
tip-slots is?

Good question. I don't know.

Don