Bulletin - United States National Museum - si-pddr - Smithsonian ...

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 yellow;
bare eyelids water green; iris avellaneous; tarsus and toes yellow
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, Uruguay,
February 19 (two males, two females) ; Tapia, Tucuman,
April 6 to 13 (two males April 8 and 9). A specimen from Kilometer
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.