Hi All,

Jim Barton writes:

> Friends--On and off for many years, red-tinted Semi-palmated
>Sandpipers >>Calidris pusilla<< have been seen at the end of Plum Island
>in Newburyport, MA. I've seen them on two occasions which I can
>remember. I've just heard of a similar red-tinted bird from Maryland,
>confirmed as Semi by the late Claudia Wilds.
>
> To the unwary, such red-tinted Semi's might suggested Rufous-necked
>Stint >>C. ruficollis<<

Jim, rufescent or rufous-morph SEMIPALMATED SANDPIPERS Calidris pusilla are
invariably juvenile-plumaged birds, and are a fairly common feature (~10%)
of the southbound migration (fall migration? heck, it's only June!) of this
species, at least at Vancouver BC Canada , where they begin to show up in
mid-July (average juv SemiSand arrival is July 17 here).

As to juv SemiSandpiper' similarity to other southbound small-Calidris
species in juvenile plumages, unlike the 'classic' juv Semi, most of the
rufous-morph SemiSandpipers have clearly-split superC's, distinctly narrow
crown stripes (rather than the conventional cap without lateral
crown-stripes), richly-fringed and -edged scaps, tertials and coverts, and
crisp mantle and scapular 'V's as conspicuous as any on a LITTLE STINT C.
minuta. In fact, on my reading of the literature combined with many years'
observation at Iona, rufous-morph SemiSandpipers are much closer to Little,
somewhat less to RED-NECKED STINT C. ruficollis, *in almost every feature
except palmations*. I have been there when Brit birders quite familiar with
juv Little have at first glance mis-ID'ed a strongly-rufous, well-marked
SemiSandpiper as a 'typical' Little, and have correctly called Semi only
after a very long, exhaustive study: that's how similar rufous-morph
SemiSandpiper can be to a typical rufous-morph Little.

Such difference from the 'classic' SemiSand juv plumage made me wonder if we
may have been looking at a possibly-undescribed race within the species or
even possibly a new species masked by similarity to the classic form, but in
personal correspondence with Dennis Paulson, discarded those ideas after he
pointed out that the rufescent form--which he describes in his excellent
book Shorebirds of the Pacific Northwest--is not restricted to a geographic
area but is generally distributed across the species' entire continental
southbound migration and that there's no corresponding difference in adult
plumages. But I'm still not 100% sure why one morph has such drastically
different plumage features (split-supercilia, bright mantle V's) to the
other, and wonder if it's still perhaps not worthwhile to speculate for the
fun of it that there's two separate species differing only in juvenile
plumages to account for the difference.

Another possibility I'd wonder about is that both Little and Semipalmated
were much more closely related before the last glaciation, or that one
species occupied the other's territory as well as its own in prehistoric
times, and that whether what we're seeing in these rufescent SemiSandpipers
is the expression of fossil Little Stint genes. Only a hypothesis.

Michael Price
Vancouver BC Canada
mprice at mindlink.net