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Re: alula

In a message dated 6/12/99 1:18:50 PM Eastern Daylight Time, 
sarima@ix.netcom.com writes:

<< Some, but not all, leading edge slats function like the avian alula by 
creating a slot at the leading edge of the airfoil.  Air forced through this 
narrow slot increases in velocity over the top of the wing, thereby avoiding 
a stall. That is essentially how an alula works. >>

I'm surprised that a small clump of feathers can divert enough air over the 
top of the wing to make a substantial difference.  Am I correct in assuming 
that in flight (as opposed to landings) these flaps are used primarily when 
the bird is climbing?  Because the original observation was about eoalulavis 
being the first bird with real maneuverability in flight, I had thought turns 
were involved.
Also, does anyone know when the alula definitely was present in the line 
leading to modern birds?  If the alula is essential for birds spending much 
of their time in flight (?), wouldn't that mean that prior birds spent much 
of their time close to the ground even if they were otherwise adapted to 
flying?  Is the alula in fact a significant indicator of bird behavior?