BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 273 



scribed by Lillo as S. dineJUi.*^ The tips of the tail feathers are 

 rounded and do not display the acuminate points found in hudsoni 

 and anthoides, a condition that may change with age. Hellmayr*^ 

 has indicated that S. lilloi is the bird described by Chapman ^^ from 

 above Tafi del Valle, Tucuman, as Siptornis punensis rufala. 



The individual taken was flushed among tussock grass that cov- 

 ered an open slope at the summit of the cumbre, and was killed on 

 the wing. It appeared dark in color when in the air, with a distinct 

 reddish-brown band in the wings. A bird of similar appearance 

 that I flushed but did not secure in tussock grass on the highest 

 points near El Salto above Potrerillos, Mendoza, during March was 

 probably Siptornis anthoides. 



SIPTORNIS HUDSONI (Sclater) 



Synallaxis hudsoni, P. L. Sclater, Proc. Zool. Soc. London, 1874, p. 25. 

 (Conchitas, Buenos Aires.) 



Hudson's spinetail in general coloration suggests a pipit, while 

 in attitude and habits it is strongly suggestive of the allied Anum- 

 hius. It was encountered at only two localities in the Province of 

 Buenos Aires, first near Lavalle, Buenos Aires, where it was fairly 

 common in marshes on October 23 and November 6 and 9, 1920, and 

 a second time near Guamini, where, on March 8, 1921, I found three 

 in a dense patch of thistles and other weeds on the shore of the 

 Laguna del Monte. Near Lavalle the bird was partial to marshes 

 grown heavily with Juncus acutus, a sharply pointed rush that grew 

 in clumps with little runways between. The birds were shy and 

 secretive and were seldom seen until they darted out and flew 

 rather swiftly with undulating flight to new cover. When once 

 under shelter they crept rapidly away so that it was difficult in 

 many instances to flush them a second time. The light outer margins 

 of the tail showed prominently in flight. Occasionally one perched 

 quietly among dead rushes at the border of some lagoon. 



On the evening of November 6, while setting a line of mouse traps 

 among hollows between the dunes south of Cape San Antonio, I 

 flushed one of these birds from the base of a clump of Juncus and 

 after careful search discovered a nest, a domed structure placed 

 directly on the ground in the base of the tussock of rush, with a 

 runway like that of some mouse leading into it. Never have I 

 seen the nest of a bird more completely concealed from any possible 

 view, and save for the chance that directed my hands to the base of 

 the clump in question, so that the female flew out almost in my 



" Rev. Letr. Cienc. Soc. Tucuman, vol. 3, July, 1905, p. 53. 



*- Arch. Naturg., vol. 85, November, 1920, p. 72. 



*3Bull. Amer. Mus. Nat. Hist., vol. 41, Sept. 1, 1919, p. .'?28. 



