Subject: Vaux's swifts' flight
Date: Aug 7 05:36:33 2002
From: Constance J. Sidles - csidles at mail.isomedia.com


Hey tweets, The thread on high-altitude Vaux's swift flight has been
interesting. Wayne Weber postulated that the swifts we saw were lower down
in the sky than the swifts we usually see at the Fill, and hence they only
seemed to be flying faster. I don't believe this is the explanation. The
swifts at the Fill fly at all altitudes. I've seen them skimming across the
main pond to grab a drink, as well as soaring so high I can hardly see
them, and everywhere in between. The swifts near Cayuse Pass were flying at
tree height or just below the treetops most of the time, but now and then
one would dip much lower. So their flying height was quite comparable to
the Fill (where the swifts often circle just above the cottonwood grove
near the east entrance). But their faster speed was notable - John and I
were trying to track them with our binoculars and could not do it. We would
fasten onto a bird and then it would change direction so quickly that it
became lost to view. This happened continuously. John and I must have given
the passing motorists quite a show, as we whirled around and around with
our binocs attached to our faces, sometimes almost bumping into each other.
It was a dizzy experience.

Jack thought that maybe the swifts were gliding faster but traveling
through the rarified air more slowly when they flapped. I don't believe
this was true, either, although I would have to think about it quite a bit
as it wasn't something I paid particular attention to. The reason I think
this was not happening is because the swifts were flapping so much and
gliding so little. Their flaps seemed more powerful somehow than at the
Fill. You know how a gyr's flaps seem to generate from their
Schwarzenegger-like neck muscles, moreso than peregrines' flaps (and
peregrines are no slouches)? The swifts up in the mountains reminded me of
that a little. Each flap seemed to *do* more, somehow. - Connie, Seattle

csidles at mail.isomedia.com