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154 BULLETIN 133, UNITED STATES NATIONAL. MUSEUM
and another March 5. Near Tunuyan, Mendoza, six were recorded
March 26 in company with the two species of yellowlegs. Two
pectoral sandpipers that I shot here were extremely fat—in fact,
one could not be preserved as a skin for this reason—but flew easily
in spite of their heavy bodies. None were recorded later than this
date.
Two adult females shot at Puerto Pinasco, Paraguay, September 9,
1920, were in worn breeding plumage, with no indication of molt.
A female shot at Lazcano, Uruguay, February 8, had renewed the
entire plumage save that new feathers in small amount were still in
sheaths on breast and back. A male taken at the same time had
the outer primary in either wing barely appearing and the ninth,
the adjacent one, not quite fully grown. Nevertheless the bird was
apparently in northward migration. A male taken at Tunuyan,
Mendoza, March 26, Avas in full plumage.
PISOBIA BAIRDII (Coues)
Actodromas bairdii Coues, Proc. Acad. Nat. Sci. Philadelphia, 1861, p. 194.
(Fort Resolution, Great Slave Lake, Canada.)
Three Baird's sandpipers were observed March 5, 1921, near
Guamini, Buenos Aires, in company with white-rumped sandpipers.
The species was at this time in northward flight from a wintering
ground in Patagonia.
PISOBIA FUSCICOLLIS (Vieillot)
Tringa fuscicolUs Vieillot, Nouv. Diet. Hist. Nat., vol. 34, 1819, p. 461.
(Paraguay.)
In addition to the characters of the white or dark upper tail cov-
erts and other color differences usually assigned to distinguish the
white-rumped and Baird's sandpipers, the two may be easily sepa-
rated by the form of the bill. In P. hairdii the bill tip is little ex
panded, the maxilla is elongately pointed, and the dorsal surface of
the tip is hard and smooth. In P. fuscicolUs^ on the contrary, the
tip of the bill is sensibly widened and has the surface distinctly
pitted. These distinctions, perceptible under a low magnification
lens, when once seen are recognized easily with the unaided eye and
form a valuable identification character when, for example, one has
specimens of the white-rumped sandpiper in which the dark cen-
ters of the white feathers are somewhat more extensive than usual,
or in which some of the light tail coverts have been lost and not yet
renewed in molt. In fact, in an extensive series it is not difficult to
find specimens that may not easily be separated from P. hairdii by
color alone but that are readily identified by the bill.
The same differences that have been pointed out between the bills
of the white-rumped and Baird's sandpipers serve to distinguish