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Re: Thread of Ptero size thread

----- Original Message ----- From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Sunday, December 17, 2006 2:00 PM
Subject: Thread of Ptero size thread

OK. This is personal observation, and I have no written reference. Watching hummingbirds over the years I seen them fly (or thought I've seen) what appears to be forward flight fairly frequently.

If I remember correctly, some of them are capable of crossing the Gulf of Mexico.

Looked a lot like burst-flapping to me, complete w/ characteristic non-hovering sound pattern.

Their kinematics though, are different from other birds.

hover, and am always disappointed when they stop.

Me too.

That said--

It follows from what you say that 1) they _hover_ when migrating across the Gulf of Mexico, 2)

No, I don't believe that follows. BTW, in birds, range is not closely related to size.

they use less energy hovering than level flap-flying (if they can),

That's not true either. And they can fly level, but they don't use as efficient a wingstroke as other birds.

and 3) the hovering failure density is indeed lower than their flapping failure density.

I doubt that as well.

Personally, I would have thought that 1) the (minimum) size constraint in hummingbirds would be from thermal relations rather than flight, 2) although their maximum size is currently constrained by hovering, they would essentially be unconstrained in the sense of evolutionary potential relative to flapping flight;

They would not be unconstrained for horizontal flapping flight if they are to keep their present system for hovering, which uses a different technique than other birds.

indeed free to evolve to whatever max bird size potential is, if they shift gears to soaring flight.

They've gone a different 'route', one not conducive to eventual soaring.