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---------- Forwarded message ----------
Date: Tue, 23 Nov 1999 20:10:35 -0800
From: Don Baccus <dhogaza at pacifier.com>

At 07:24 PM 11/23/99 PST, Wm Mulligan wrote:
>
> I would guess that undulating flight in small birds is
> an evasive maneuver, to avoid being picked off by larger
> predators, rather than an energy conservation strategy.

This probably wouldn't explain the sinusoidal waves such undulating
flight often scribe in the sky...it only takes a handful of neurons
for a predator to calculate an intersection course.

The up-down rythm of flickers, finches, and certain other birds
can't really be attributed to predator avoidance for this reason.

The rythm tends to be REGULAR, exactly the kind of thing predators
adapt to.

- Don Baccus, Portland OR mailto:dhogaza at pacifier.com
Nature photos, on-line guides, Pacific Northwest
Rare Bird Alert Service and other goodies at
http://donb.photo.net.