Jack Bowling wrote:

>Umm, excuse me, but that is exactly the argument here. It is pure semantics
>to conjure up some difference between "displacement of some species as a
>result of high winds" and "a hurricane sweep(ing) a bird off its perch and
>depositing it alive, hundreds of miles away". It is very likely that there
>is a threshold wind speed over which any land (and sea) bird would be
>nuked, that threshold lowering with the decreasing skeletal resiliency of
>the affected species. Where would a hummer fit in on this scale? Don't
>know. But they are tough little buggers, as are their close cousins swifts.
>We seem to have no problem accepting the fact that anything over open water
>is fair game to be swept along by a hurricane. It is very hard to believe
>that landbirds *never* get swept out to sea by storms, especially when
>considering the dearth of forest to take cover in on the narrow Baja
>peninsula. It is still quite easy to believe that the Xantus' in question
>was swept off the coast (either east or west depending on if it happened
>with the approach or departure of the hurricane), especially considering
>that Nora was winding down rapidly by the time it got to Baja latitudes,
>thus increasing the chance that its mortality threshold wind speed had not
>been maintained. Yes, there may be little to no historical precedent for
>landbirds getting towed along by hurricanes and surviving the trip, but
>that *does not* _a priori_ mean that it could never happen.

Jack, I wouldn't maintain that it could *never* happen, but my thought is
that a wind strong enough to dislodge a small (and perhaps large) bird from
its hurricane shelter (deep in the foliage) would probably do it in! I
visited the upper keys and lower Everglades National Park after hurricane
Donna in 1960, and prepared skeletons of a large series of "Great White"
Herons that were removed from the tree branches around which they had been
wrapped. The destruction of bird life was awesome. I spent a day at
Flamingo one week after the eye of the hurricane passed, and there was not
a single (evident) surviving small land bird there! Three Palm Warblers in
a parking lot were presumably migrants.

Of course Donna was a stronger hurricane than the ones that hit the west
coast of Mexico, but my gut feeling is still that weak hurricanes don't
displace land birds, while strong hurricanes kill them, the latter as you
say yourself. I don't see how anyone can argue that the lack of records of
West Indian birds associated with hurricanes on the Atlantic coast isn't
the best evidence we have against such displacements, no matter what the
semantics.

I've also seen warblers migrating off the coast of Florida fall to the sea
surface when they apparently became too tired to fly, not to rise again,
and there are many published accounts of storm mortality to migrants over
the ocean. The effort to stay aloft in hurricane winds must be tremendous
for a bird not adapted to flying under those conditions, but that's not the
whole part of my argument. My argument is still that the probability of a
Xantus' Hummingbird being swept out to sea by wind is small, but I consider
even more significant that the probability of its moving all the way north
to BC *as a consequence of that wind* is infinitesimal. I consider it quite
reasonable to draw conclusions based on probabilities, if we have no direct
evidence.

If you look at vagrant records from the PNW, you find that essentially all
of them are migratory species, no matter where their origin, and the
migratory urge, coupled with a screwed-up directional programming, can
fairly easily explain their presence. I don't think we have a good
biological explanation for the presence of a resident bird so far out of
range.

I hope we haven't run this subject into the ground!

Dennis Paulson, Director phone 253-756-3798
Slater Museum of Natural History fax 253-756-3352
University of Puget Sound e-mail dpaulson at ups.edu
Tacoma, WA 98416
http://www.ups.edu/biology/museum/museum.html