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 



