BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 359 



zorzal negro of the western Argentine will recognize it under its 

 present appellation only with difficulty. 



These black robins were encountered in the vicinity of Potrerillos, 

 Mendoza, from March 15 to 21, 1921, where seven were taken, all, 

 except one adult female, immature. The species was recorded to an 

 elevation of 1,800 meters at an estancia known as El Salto. 



A male in the spotted and streaked juvenal plumage, shot March 

 15, had the bill, in general, dull black, shading to onionskin pink at 

 lip; gape between ochraceous buff and ochraceous orange; eye ring 

 chamois; iris light drab; tarsus ochraceous buff, with a tinge of 

 gray ; nails dull black. A male partly molted into first fall plumage 

 had the bill including the gape zinc orange; eye ring mustard yel- 

 low; bare eyelids water green; iris avellaneous; tarsus and toes yel- 

 low ochre; nails dark neutral gray. The change from black to 

 yellow bill is coincident with the post-j'uvenal molt. An adult 

 female taken March 19 is in full molt. 



The present species was met in thickets in the vicinity of water, 

 either near irrigation ditches or along streams. At intervals they 

 flew from covert to covert, and after alighting might pause for an 

 instant in the open with jerking wings and tail, but at the slightest 

 alarm dropped into heavy cover. The taking of specimens was dif- 

 ficult as it was restricted to what snapshots might offer. The birds 

 were observed feeding on the berries of the piquillin {Gondalia 

 lineata). 



Family SYLVIIDAE 



POLIOPTILA DUMICOLA (Vieillot) 



Sylvia dumicola Vieillot, Nouv. Diet. Hist. Nat., vol. 11, 1817, p. 170. 

 (Uruguay.)" 



The gnatcatcher was recorded as follows: Resistencia, Chaco, 

 July 8 to 10, 1920 (a pair) ; Las Palmas, Chaco, July 13 to 31 

 (female, July 20) ; Riacho Pilaga, Formosa, August 7 to 18 (male, 

 August 7); Formosa, Formosa, August 23 and 24; Kilometer 80, 

 west of Puerto Pinasco, Paraguay, September 11, 15, and 20 (male, 

 September 11); Kilometer 200, west of same point, September 25; 

 Lavalle, Buenos Aires, October 27 to November 13 (male, October 

 30) ; San Vicente, Uruguay, January 31, 1921 (male) ; Lazcano, 

 Uruguay, February 6 (immature female) and 7; Rio Negro, Uru- 

 guay, February 19 (two males, two females) ; Tapia, Tucuman, 

 April 6 to 13 (two males April 8 and 9). A specimen from Kilo- 

 meter 80, Puerto Pinasco, is slightly smaller than others, otherwise 

 the series exhibits only the slight differences due to age, sex, or sea- 

 sonal wear. April specimens are completing a fall molt. 



e* See Dabbene, El Hornero, vol. 1, 1919, p. 240. 



