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

BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 305
in this arid region were not suited to them, so that their number was
not great.
MACHETORNIS RIXOSA RIXOSA (Vieillot)
Tyranmis rixosus Vieillot, Nouv. Diet. Hist. Nat., vol. 35, 1819, p. 85.
(Paraguay.)
Common and widely distributed through the pampas and the
Chaco, the present bird was noted at the following points :
Berazate-
gui, Buenos Aires, June 29, 1920; Santa Fe, Santa Fe, July 4; Ee-
sistencia, Chaco, July 9 and 10; Las Palmas, Chaco, July 14 to 23;
Formosa, Formosa, August 5, 23, and 24; Riacho Pilaga, Formosa,
August 21; Puerto Pinasco, Paraguay, September 1 and 30; Kilometer
80, Avest of Puerto Pinasco, September 6 to 21 ; Lavalle, Buenos
Aires, October 23 and November 9; Montevideo, Uruguay, January
14, 1921 ; La Paloma, Uruguay, January 23 ; San Vicente, Uruguay,
January 27 to Februai-y 2 ; Lazcano, Uruguay, February 5 to 9.
The sj^ecies was most abundant in the Chaco, and was not recorded
in the arid interior sections of central Argentina. An adult female
taken at Formosa, AugTist 24, and a pair secured at the Estancia
Los Yngleses, Lavalle, Buenos Aires, on Novemb r 9, resemble other
skins examined from Paraguay and southern Brazil. 31. r. flavogu-
laris Todd.^^ named from Venezuela, of which I have seen no speci-
mens, is said to be brighter below than rixosa, with the throat but
little paler than the abdomen, while the gray crown is duller, con-
trasting less strongly with the back. This form is said to occupy
all the northern portion of South America.
These flycatchers inhabit wet localities in open regions, where
occasional trees offer suitable night roosting places, a predilection
that explains their greater abundance in the Chaco, where wet
savannas with scattered trees are the characteristic feature of the
country. Machetornis, though it roosts at night among leafy
branches, spends most of its day on the ground, preferably near or
among horses, cattle^ ov sheep that it follows as assiduously as do
cowbirds for the sake of insects frightened up or attracted by the
feeding stock. It is common to find Molothrus and Machetornis in
company in suitable situations, and the flycatcher flies up to perch
on the back of an ox or a horse as fearlessly as on a log or a post.
In fact, the birds shoAved preference for such perches and frequently
alighted on an animal when frightened from the ground. The ordinary
method of progression of this bird was peculiar. A long,
hesitating step made with bobbing head, was followed by a run for
four or five steps, then another long step with the run repeated. In
pursuit of insects or to evade too familiar approach it often ran
8* Ann. Carnegie Mus., vol. 8, May 20, 1912, p. 210. (Tocuyo, Estado Lara, Venezuela.)