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

82 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
tion. A number were observed exposed for sale in the markets of
Buenos Aires at the end of June. No specimens were secured.
METOPIANA PEPOSACA (Vicillot)
Anas peposaca Vib^llot, Nouv. Diet. Hist. Nat., vol. 5, 1816, p. 132. (Paraguay
and Buenos Aires.)
The rosy-billed duck was one of the common species found in the
region surrounding LaA^alle, Province of Buenos Aires, from Octo-
ber 23 to November 9, 1920. The birds frequented open pools in
the marshes where the water stood from a few centimeters to a
meter or so deep, and though not averse to frequenting small ponds
surrounded by high vegetation did not penetrate among the rushes.
In form and habits the species is closely similar to the American
redhead {Marila arnericana), a species from which it is not dissimilar
in color pattern aside from the prominent rosy-colored knob
developed on the bill in males'. Females, when on the wing or when
resting on the water, resembled female redheads closely, but were
marked by the sharply outlined white under tail coverts that made
a prominent field mark. The flight was swift and direct, and birds
showed entire lack of fear of any object not wholly visible to them,
so that to secure a shot it was often only necessary to crouch in the
grass or rushes when they were circling on the wing.
At this season rosy-billed ducks were found in pairs or were engaged
in mating. Frequently four or five males swam in pursuit
of one female, who remained in the lead while in turn her suitors
rose to flutter along for several meters with the rear portion of the
body dragging on the surface of the water. The note of the male
is a purring kah-h-h, a low call that carries for only a short distance.
On December 3 several were found on quiet channels and lagoons
near the Rio Negro below General Roca, Territory of Rio Negro.
Others were noted at Carhue, Buenos Aires, December 17, and on
February 6, 1921, the species was seen in a large marsh near Laz-
cano, in the Department of Rocha, Uruguay. On February 8, at
Lazcano, I examined a young bird three-quarters grown that had
been killed recently by some gunners. This bird displayed dull
markings slightly darker than those of the female, especially on the
breast. In form it showed the strong, heavy leg muscles character-
istic of the young of deep-water ducks, while the muscles of the
breast were thin and undeveloped, though the wing quills were half
grown. Two adult males were observed at Rio Negro, in westcentral
Uruguay, on February 16. The species is commonly known
as pato picaso.