Kimball Garrett's message sent to Frontiers was forwarded to me, and I want
to add a few comments.

I was glad to see his commentary on (lack of) structural differences
between Whimbrel and Bristle-thighed. I looked at large series of both of
them when I wrote my shorebird book and could find none. And now I've
finally had the pleasure of seeing that elusive Bristle-thighed, alive and
upright! I spent a half-hour watching one of each foraging and standing
together on the beach at Ocean Shores, WA, yesterday, really looking hard
for structural/shape/posture/behavioral differences and failing to see any.
The two birds looked as identical as peas in a pod except for their
relatively few plumage differences.

If I had been forced at gunpoint to describe a structural difference, I
would have focused on the legs and feet. The legs of the BTCU did look very
slightly shorter (and Kimball's tibiotarsus measurement indicates this),
but of course another pair of birds might have looked different. And I did
feel that maybe, perhaps, there *might* have been an indication that the
BTCU had slightly heavier feet than the WHIM, and it sounds as if others
noted this difference as well. If many BTCUs spend a lot of time on coral
atolls, heavy feet (fat toes) would be a good adaptation, just as
characterizes a number of rock shorebirds. And, of course, relatively short
legs also characterizes rock shorebirds.

The bill of the BTCU was about half the height at the base as that of the
WHIM, but I assume this might be a sexual difference, as Ruth Sullivan's
photos of two BTCUs in Oregon show exactly the same difference between
those two individuals. Oddly, I could detect no difference in bill length,
although I would have thought the thicker-billed bird would have had a
perceptibly longer bill. According to Kimball's measurements, the average
female WHIM should have a bill about a half-inch longer than the average
male BTCU, but of course who ever sees average birds?

I was surprised by Kimball's comments on the relative quietness of these
birds. The Ocean Shores BTCU called as it flew in, calling attention to
itself; it called every time I or anyone else approached it; and it often
seemed to be calling spontaneously. It gave its 3-noted whistle 20+ times
while we watched it, as well as a few other 1-2-noted calls. The WHIM never
uttered a peep (or pip). Ruth Sullivan told me she heard one or more of the
OR birds calling frequently. The first birds seen in WA, the pair seen by
Bob Sundstrom and Hal Opperman, called so loudly and frequently that the
observers were finally forced to take a look at the assumed "Black-bellied
Plovers" flying behind them, leading immediately to the birders' UFO
(uninhibited freak-out) syndrome.

I had never heard even a recording of the bird before, and one of the major
thrills of seeing it for the first time was hearing it. When you have
handled dozens of skins and looked at plenty of photos, you almost feel
that you have seen a bird already, but hearing the call is a real
adrenaline rush, especially as I had always hoped I had described it
correctly in my book! I described it as "less plaintive than a
Black-bellied Plover," and it is actually a whole lot less plaintive, a
really sharp (and, as Kimball wrote, human-sounding) whistle. And a really
sharp bird!

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