Re: hovering diversity (was Re: Ornithurine diversity)

[Michael Habib <mhabib5@jhmi.edu>]

> For my observations, I've got to go with the updraft explanation.
> Unless by "long time":

I do as well - in the cases of kiting by bluffs or cliffs, as you 
described, the animals are almost certainly using deflected flows.

> ] you simply won't notice the sink rate unless you watch one for a
> ] long time
>
> you mean something on the order of minutes, hours, or days...

Minutes, in that case.  Again, though, it only applies to cases where 
there is no orographic lift involved.  My point was to demonstrate what 
happens in the most simple situation, and why even that case can give 
the appearance of zero sink.  An actual zero sink situation obviously 
requires a lifting condition.

> In what I've seen it appears the birds don't so much appreciate the
> gusts.  It is, of course, gusty around here (I've had cause to worry
> about getting blown off the bluffs...), but when it gusts is when you
> do see the birds move.

It depends on the situation, naturally.  If they're staying steady in a 
deflected flow, then a strong gust might be disadvantageous.  However, 
gusts also represent a source of energy that can be utilized to stay 
aloft or reposition for low cost.

Cheers,

--Mike


Michael Habib, M.S.
PhD. Candidate
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205
(443) 280 0181
habib@jhmi.edu