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

BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 375
and circled uncertainly for a meter or so, undecided where to go. I
shot one of these and the other immediately dropped into the grass
beside it to share its fate a moment later. Loss of the sentinel
thus broke up for a few minutes the entire flock organization.
Early in morning long, straggling flocks were observed in flight
across country to favored grounds. In feeding, the birds remained
hidden in cover of the grass, and were difficult to see until they rose.
In flight they often mount for 30 meters in the air and start as
though bound for some distant point, but suddenly pitch down into
the grass perhaps not more than a hundred meters from the point
where they flushed.
In certain areas they seemed to be on their breeding grounds,
though no nests were found. In these localities males rested on
clumps of grass or on fence posts, where they displayed their bril-
liantly marked breasts. At short intervals they rose from 1 to
2 meters in the air to give a high-pitched song and then with spread
wings set stiffly above the back dropped rapidly to the ground with
a shrill, rattling call. Females remained under cover, and when
flushed hid at once in the grass. The call note of the males was a
note like chej)^ while females uttered a low, chattering call. At
times males pursued females swiftly over the prairies.
The black under wing surface of the present species is easily
seen when the birds are in flight and distinguishes it readily from
T . rtiilitaris in which the under wing coverts are white.
LEISTES SUPERCILIARIS (Bonaparte)
Trupialus superciliaris Bonaparte, Consp. Gen. Av., vol. 1, 1850, p. 430.
(Matto Grosso, Brazil."*)
An adult female shot at Formosa, Formosa, August 24, 1920, was
the only skin preserved, as a male killed September 25 at Laguna
Wall, 200 kilometers west of Puerto Pinasco, Paraguay, was through
force of circumstances made into a skeleton. Bangs ^^ has named a
southern subspecies of this bird as j/et'dus (type locality Concepcion
del Uruguay, Entre Rios), but with the scanty material of this
species at hand I am unable to make out geographic forms. The
female recorded above has a wang measurement of 88 mm. Hellmayr
'° indicates superciliaris as a race of Leistes viilitai'is. The
presence of a distinct superciliary in the male of the southern
bird seems to indicate specific distinction between the two.
The present species was seen on comparatively few occasions. The
first one was recorded near Santa Fe, Santa Fe, on July 4, 1920 ; one
was seen later in July at Las Palmas, Chaco (date uncertain) ; a half
«* See Berlepsch, Nov. Zool., vol. 15, June, 1908, p. 123.
«>Proc. Biol. Soc. Washington, vol. 24, June 23, 1911, p. 190.
Arcli. fur Naturg., vol. 85, 1919 (November, 1920), p. 34.