Re: Thread of Ptero size thread

[jrc <jrccea@bellsouth.net>]

----- 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.