** Reply to note from Deb Beutler

> The phalarope question started the wheels spinning in my head.
> I think we can rule out the Coriolus effect. Why would they care or
> be affected since it is such a weak force?

The Coriolis Effect is not really a force - it is an effect due to the changing angular
velocity of the earth's rotation with latitude, acting to the right of a particle's
trajectory in the northern hemisphere and to the left of the trajectory in the southern
hemisphere. As such, the small linear distances involved underneath a phalarope would
not allow for much if any Coriolis Effect. Oh and just for the record, I tried the "draining
water basin effect" in Sydney, Australia and it indeed did drain with a clockwise rotation.

> It might be a genetic thing. People are right or left-handed; maybe
> phalaropes are the same way, only with spinning. Crossbills are left or
> right billed, but that is morphological (the bill is crossed with the top
> either on the left of right, making it easier to extract pine seeds from one
> side of the cone resulting in both side of the cone being eaten (at least
> that is how it was explained to me). Maybe spinning in different directions
> allows phalaropes to split their niche.
> Maybe they alternate. One time they go left, next time they go right.
> Maybe it is a social thing. Perhaps feeding is more efficient if
> all of the birds are spinning the same way.
> So watch those phalaropes and tell me how they are spinning (I will
> have to wait several weeks before I can make any observations!)

Another possibility is that clockwise or counter-clockwise vortices may be favored
depending on both existing vertical density gradients and horizontal currents of the
water column beneath a spinning phalarope. The bird tries it one way for a while and
then the other, eventually settling on the one which incurs the greatest vertical motion.
Note that this would likely change with time and thus would the bird's preferred rotation.

- Jack



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Jack Bowling
Prince George, BC
jbowling at direct.ca