Re: Altitude effects on hummingbird flight?

[don ohmes <d_ohmes@yahoo.com>]

----- Original Message ----
From: jrc <jrccea@bellsouth.net>
To: d_ohmes@yahoo.com
Cc: dinosaur@usc.edu
Sent: Thursday, December 21, 2006 11:04:58 AM
Subject: Re: Altitude effects on hummingbird flight?


----- Original Message ----- 
From: "don ohmes" <d_ohmes@yahoo.com>
To: <dinosaur@usc.edu>
Sent: Thursday, December 21, 2006 9:55 AM
Subject: Altitude effects on hummingbird flight?


> Hummingbirds are the largest observed species using hovering, a
> size-constrained locomotion;

No, a number of other, much larger birds use hovering -- but they do it by 
means of a different technique, full momentum reversal (the flutter stroke). 
You will see hawks doing it regularly while hunting, and they are for the 
most part, larger than hummingbirds.

------------- Not as a primary form of locomotion, they don't. Especially in 
still air. If you define "hovering" as "remaining stationary relative to the 
ground", yeah, lots of stuff "hovers", especially in moving air. Perhaps I 
should have said, "largest observed species using hovering as a primary form of 
locomotion...", but as I was discussing evolutionary scenarios, I didn't think 
it necessary. IIRC, Pennycuick says pigeons are about maximal for "hovering" in 
_still air_, and that is momentary (less than 4 min), not primary. Unless it is 
a functional bottleneck relative to ecology, it seems unlikely to control 
flight morphs...


> if some "un-related" group of similar size
> evolved hovering, it seems to me that a high degree of convergence
> would be expected.

There is another small african species that regularly hovers (I forget its 
name), but it doesn't fly backwards and doesn't suppinate the wing to the 
extent that hummingbirds do.  Other, larger species hover by means of a very 
different technique -- no convergence.

------------ No functional equivalence, no convergence. Not a primary form of 
locomotion, no equivalence. The African species sounds interesting. On my list 
of things to do.

> In either case, I wonder what could have knocked
> them out? Given that hummers occur in Alaska, it astonishes me that
> they never got a foothold in Asia. Anybody know got a clue?

Nope, not a clue.  I'd expect  'em to spread as well.  They are very good at 
what they do.

------------- It all seems downright weird to me.

------------ Don

JimC