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

BIKDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 271
ground where it was difficult to reach it. This nest was composed of
firmly interlaced thorny twigs that made a ball 200 mm. in diameter.
At one side near the top was an entrance opening, located among
thorny limbs of the shrub, and further protected by small spiny
twigs grouped about it. After some difficulty I opened the stinicture
to find that the interior cavity was firmly and closely felted with a
lining of fur from the introduced hare, a device that not only made
B, safe cushion for the eggs and young, but also gave protection
from the severe winds of this region, that otherwise had free passage
amid interstices in the nest material. This nest contained two
white eggs, that when first seen were beautifully tinted by the yolk
within through the somewhat translucent shell. When blown they
became dull white in color. These eggs measure as follows, in millimeters:
18.4 by 14.4, and 18 by 14.6. In form the eggs are rather
bluntly pointed with little distinction between large and small ends.
It is probable that tAvo broods are reared in a season, as young only
recently grown were taken in March.
SIPTORNIS PATAGOKICA (d'Orbigny)
Synallaxis patagonica d'ORBiGNY, Yoy. Amer. Merid., Ois., 1835-1844, p.
249. (Banks of the Rio Negro.)
Near General Koca, Rio Negro, from November 23 to December 2,
1920, the present species was fairly common ; adult females were collected
on November 23 and 24 and a male on November 25. The
skins preserved do not differ appreciably from two taken near San
Antonio del Oeste, not far from the type locality. The species has
been recorded west to the Rio Limay in Neuquen,*° a short distance
beyond Roca. The throat in patagonica of both sexes has the
feathers slate at the base with the tips white, forming a distinct dark
throat patch spotted rather irregularly with white, as prominent as
the throat patch of Synallaxis f. frontalis. No mention of this is
made in the description in the British Museum Catalog (vol. 15,
p. 69), and in the key (p. 65) the throat is said to be unspotted,
though the original description by d'Orbigny describes the throat
as distinctly marked. The species differs notably in structural characters
from the stiff-tailed forms of Siptornis and in some ways
seems quite aberrant.
This bird was found in the semiarid region that bordered the Rio
Negro, where it frequented the denser, taller stands of Atriplex and
other shrubs that grew in the river bottom or occurred more spar-
ingly in the smaller, more scattered growth that clothed the gravel
hills above the flood plain. Individuals hopped about among the
twigs or walked slowly around on the ground, always under protec-
"Hellmayr, Nov. ZooL, vol. 28, September, 1921, p. 268.