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

BIKDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 49
Near General Roca, Rio Negro, on November 27, one was seen
breasting the swift current of the Rio Negro in main stream. On
January 9, 1921, in the mouth of the Arroyo Carrasco, below Monte-
video, I found two pairs apparently on their breeding grounds.
When I first arrived only two grebes were visible, but these were
joined at once by two others, one of which came sliding out from the
reeds on the opposite bank. The birds, handsome in their full
plumage, swam back and forth with arching necks and raised crests,
finally diving as I came out from cover of the bushes. Two others
were seen offshore in salt water opposite Carrasco on January 16.
while near Lazcano, Department of Rocha, Uruguay, two in full
plumage were noted February 7. On March 4 one was recorded on
the Laguna del Monte at Guamini, Province of Buenos Aires, Ar-
gentina.
It is probable that birds from Patagonia and Chile may be sep-
arated from those from Buenos Aires, and farther north by smaller
size, smaller, more slender bills, and in adult plumage, by grayer hind
neck. The series at hand, however, is insufficient to make these
points certain.
PODILYMBUS PODICEPS ANTARCTICUS (Lesson)
Podiceps antarcticus Lesson, Rev. Zool., July, 1842, p. 209. (Valparaiso.)
The pied-billed grebe of southern South America may be segregated
from typical podiceps of North America as a subspecies under
the name antarcticus of Lesson, on the basis of average grayer colora-
tion above, including sides of neck, and more brownish hind neck.
It is a large robust form with strong, heavy bill. Specimens have
been examined from Buenos Aires, Rio Negro, and Chubut, Argentina,
and Santiago, Chile, but whether this form covers the whole
of South America remains to be determined. Females of this species
in breeding dress may be distinguished from males by the greater
extent of the dusky markings on the feathers of the undersurface,
especially on the lower breast and abdomen, so that they appear
much darker, a point that needs attention in making comparisons.
Following are measurements, in millimeters, of three specimens taken
near General Roca, in the Territory of Rio Negro, Argentina :
Two
males, wing 136.5, 145.0; culmen, 25.6, 25.0; tarsus, 45.5, 46.0; one
female, wing, 133.8 ; culmen, 22.5 ; tarsus 42.5.
Near Lavalle, Province of Buenos Aires, from October 30 to November
9, pied-billed grebes were seen at intervals in pools in the
marshes. They were very shy and seemed to be on their breeding
grounds. At General Roca, in Rio Negro, they were found in the
quiet water of narrow lagoons, bordering the present channel of
the river. On November 30 I killed three here, a mated pair and a
fully grown male still in immature plumage. The adult male taken