Re: WING FEATHER ATTACHMENT

[Michael Bruce Habib <mbh3q@cms.mail.virginia.edu>]

I have a couple of questions/comments regarding gliding, 
and the glider thread...

Firstly: Would having a discontinuous wing surface provide 
enough resistance to make any difference?  If the only 
gliding surface we are considering is distal wing elements, 
I don't see how it would make any difference.  If anything, 
the arms would be forced back towards the shoulders, and 
the animal would twirl around. Modern gliders all use broad 
surfaces across all four limbs, so that the braking force 
is applied across most of the animal and a broad membrane. 
Otherwise, the creature just spins.

> But for improved maneuverability to be the major selective advantage behind 
> the development of the primordial wing, a *slower* airspeed would be better, 
> wouldn't it?  The aim is not so much to travel a long distance but to land 
> with greater precision

Absolutely.  Gliding is not unpowered flight, it is slowed 
falling.  Modern gliders slow their rate of descent such 
that they have time to steer, are going slow enough to 
steer, and (most importantly) don't break themselves upon 
landing.  Gliding possums, squirrels, and others all show 
this same technique.  All of these gliders have very low 
terminal velocities in free-fall, thanks to the gliding 
surface.  It is important to note here that gliders 
therefore need vertical falling room.  A long glide takes 
an animal long horizontal distances, but also a significant 
vertical distance downward.  That is, while it going 
forward more than down, the animal must land lower than it 
takes off.

The distances are determined by the launching force and  
available vertical drop distance, not by how fast the 
animal glides. 

One last note: I don't believe any modern gliders glide 
onto prey items.  Gliding possums will pounce over short 
distances (a couple feet) to hit insects, and are very good 
at it, but long glides are transportation only.  (This is 
based on personal observation only).

Michael Habib
mbh3q@virginia.edu
Student, Biology Department
University of Virginia