Subject: shorebird overflights
Date: Sep 30 14:05:20 1994
From: Dennis Paulson - dpaulson at ups.edu


I have been exceptionally busy this week so haven't got into this
discussion, but I'll put in my two cents briefly. I think sampling bias
probably explains most of the differences in number of records of rare
shorebirds. Certainly, as David Wright pointed out, there are more such
records from Iona Island, BC (especially if you add Boundary Bay to it),
than from the entire WA and OR coasts. This is off the top of my head, I
haven't tallied them. If someone wants to do so, there is a book called
_Shorebirds of the Pacific Northwest_ that contains the requisite
information for BC, WA and OR. I for one would be interested in the
results.

There should indeed be a concentration of records of vagrants from the
latitudes in which they winter, whereas birds just passing through (and not
being familiar with the local scene) might stop anywhere. *However,*
essentially all of the shorebirds we consider vagrants winter at latitudes
to the south of California--in the Asian tropics or Australia. So the
California birds aren't at their wintering latitudes, although there are,
of course, extremely few records of Old World shorebirds on the tropical or
southern-hemisphere shores of the Americas (far, far too few observers). I
would say "wintering latitude" is rejected, and "sampling bias" remains a
viable hypothesis.

Dennis Paulson