In a message dated 96-01-02 20:12:27 EST, Gene Hunn writes:

>
>I've noticed that gulls and shearwaters almost always circle the pelagic
>boats counterclockwise. Do they circle clockwise south of the Equator?
>
>

Well, we're certainly not doing crossbills at this point. Hmmm. Actually I
had to stop and think about that. Can't say I've really noticed anything I'd
call Coriolis inflicted seabirds. However, I believe that their direction of
flight relative to a vessel is more wind dependent than anything. If the
winds are not storm or hurricane force, then they tend to fly into the wind
which could be clockwise or counterclockwise depending on which way the boat
is steaming relative to the wind...same as in the northern hemisphere.

In the southern hemisphere, 30's, roaring 40's and furious 50's, the
prevailing winds and seas are westerlies. If the vessel is southbound, they
circle counterclockwise; if northbound, then clockwise. Of course, the birds
have to be circling as ship followerers like albatrosses, cape petrels,
prions, et.al. often do. And then there are those which just course back and
forth in the wake endlessly to which all this seems to be of no concern to
them.

The one thing that is different in the southern hemisphere of course is wind
direction relative to LOW and HIGH pressure areas -- it's reversed (Coriolis
effect) -- but still that has no direct link to a seabird's predisposition to
fly clockwise in the southern hemisphere to their counterparts flying
counterclockwise in the north.

Like the in the southern 30's, 40's, and 50's latitudes, the prevailing winds
and seas in the same northern latitudes are westerlies. With that in mind,
chances are you may be more tuned to the counterclockwise flight on a trip
out of Westport then on the way back. On the other hand, if you are paying
attention and the birds continue to fly counterclockwise, perhaps they have
just gotten habituated to the routine relative to the boats orientation to
them. I think seabirds are first drawn in toward the stern where all the
wake disturbance (and chumming) is taking place and the circling if there is
any commences from there, i.e., counterclockwise and into the wind. By doing
so, they have more control for dropping suddenly into the slick or
disturbance if they are flying into the wind, no matter how light. Passing
then before the bow, they are just *coasting* downwind to get lined up for
another pass at the wake. If there is no wind at all, then I venture to
guess that the circling direction probably doesn't make too much difference.
If the boat happens to be stopped, the Captain may have a preference to
putting one side of the boat to the wind over the other. If that happens to
be the starboard (RIGHT) side, in which case, birds coming up on the wake off
the stern would circle if so inclined, counterclockwise.

In the tropics, boobies provide endless entertainmentand amusement. They
ride the deflected wind currents on the windward side of the bow constantly
vigilent for flying fished disturbed into flight. Brown and masked boobies
will chase a flying fish then dive on them just as they hit the water. I've
seen them fly through waves, coming out the other side still in flight with
the prize in their bill. Red-footed boobies seldom dive for their prey,
rather snatch their flying fish out of mid-air. Here, I've digressed
(again), but the point is, clockwise vs counterclockwise, north or south,
makes little difference. It's all dependent on wind, whether real or
relative.

As for being chicanerous Dennis, I wonder now if that's what this thread was
all about in the first place. Hmmm. From ospreys to crossbills to seabirds.
I really should have been doing something else instead of posting on
this...like watching StarTrek, or God forbid; a football game.

Richard Rowlett <pagodroma at aol.com>
Bellevue, WA, USA