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BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 229
plumage on the throat, with more feathers of the same color in
process of groAvth aromid it. The male until it dons adult plumage
has a white spot behind the eye like that found in females. Imma-
ture birds of both sexes are duller above than adults.
Present understanding of the geographic forms of ChlorostiJbon
aureo-ventHs is highly unsatisfactory. Simon has described a
southern form,^ including a range from southeastern Brazil to
Buenos Aires, but has complicated matters by calling egregius a
form of C. 'prasina. The subspecific variations of aureo-ventris
must for the present remain clouded in doubt.
ChloTostUhon aureo-ventris was recorded at the following points:
Riacho Pilaga, Formosa, August 11, 14, and 18, 1920; Lavalle,
Buenos Aires, October 29 to November 15; San Vicente, Uruguay,
January 26 to February 2, 1921 ; Lazcano, Uruguay, February 3 to
9 ; Rio Negro, Uruguay, February 14 to 19 ; Tapia, Tucuman, April
7, 8, and 13. Individuals were seen during July, 1920, near Las
Palmas, Chaco.
During winter these hummers were encountered occasionally at
the border of forests and thickets, where they received the warmth
of the sun and were protected from cold winds. Small shrubs that
were in flower were frequented, and I saw them gleaning insects
from the limbs of trees. In the pampas during summer hummers
came in small numbers to flowers about the estancias or occasionally
dropped down into the inclosed patios of small country hotels. On
January 26, near San Vicente. Uruguay, a female flashed by me in
a forest of palms, and on glancing up I caught sight of her nest
placed on a swinging bit of fern root, 12 feet from the groimd, below
the crown of leaves that formed the top of the tree. To my
great disappointment the nest was empty. It was of the usual hummer
type, a soft, cup-shaped structure made of plant downs and
fine bark, covered with fragments of brown bark fastened in place
with spider webbing.
Near Tapia, Tucuman, this hummer, with others, frequented the
red flowers of an abundant epiphyte {Psittacanthus cuneifoUus).
A female, taken August 14, had the tip of the bill black, and the
basal half orange-cinnamon, the two colors blending at the point of
junction; iris Rood's brown; tarsus and toes fuscous; nails black.
OREOTROCHILUS LEUCOPLEURUS Gould
Oreotrochiliis leucoplenrus Gould, Proc. Zool. Soc. London, 1847. p. 10.
(Chilian Cordillera.)
Near Potrerillos, Mendoza, two females were secured on March
16 and 19, 1921. This species is more sluggish in its movements than
» ChlorostWbon aureiventris tucumaniis Simon. Hist. Xat. Troch., 1921, p. 65.
(Tucuman.)
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