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. (Para- 

 guay 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 dis- 

 similar 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 en- 

 gaged 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 west- 

 central Uruguay, on February 16. The species is commonly known 

 as pato picaso. 



