On Sat, 31 Jan 1998, Jack Bowling wrote:

>
> Bill Smith writes -
>
> > >Dispersal of survivors trying to deal with the impact of a storm or other
> > >phenomena like volcanic eruptions on food sources, after the fact, is
> > >another issue, but I'm not aware that off-island displacement has ever
> > >been proven even in that more likely scenario. There may also be some
> > >displacement of some species as a result of high winds, but that's not
> > >quite the same as saying that a hurricane sweeps a bird off its
> > >perch and deposits it alive, hundreds of miles away.

Jack Bowling:
> 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.


I'm not exactly sure what you mean by high winds "nuking" a bird, but I'll
agree about hummers being tough enough little buggers to survive just
about any imaginable wind: What you didn't point out but may have been
thinking is that to a bird in flight, a 100mph wind is not necessarily a
big deal. The 100mph figure refers to the speed of the wind over the
ground, whereas the bird, once in flight, is moving at the speed of the
air around it. A hot air balloon rider on a windy day doesn't feel the
wind constantly blowing past him; he just gets carried faster over the
ground. It feels calm where he is, unless he passes a boundary
from one moving parcel of air to another moving in another direction. The
only way a flying bird could get "nuked" by wind is if there was small
scale turbulence within the moving air that was powerful enough to do
harm, which seems unlikely if we're talking about "skeletal resilience."

I'd think precipitation, and the simple endurance of the bird ("how long
can you tread air?") would matter much more than the strength of the storm
as measured by windspeed.

Christopher E. Hill
Department of Zoology
University of Washington
P. O. Box 351800
Seattle, WA 98195-1800