348 Mr. C. H. B. Grant on Birds collected in Argentina , 
The only difference between the pair of: young shot in 
December lies in the male having a considerably darker 
speculum ; both are moulting on the back. The young 
female taken in April is moulting all over, except for the 
wings, and bas already assumed the rufescent head, breast, 
and back feathers of the adult ; the speculum is pale 
brown, blackish where it adjoins the light tips and on the 
inner webs. 
This is perhaps the commonesti Duck on the pampas of 
the Ajo district; at the time that the thistle-seed is ripe 
(January to April) enormous flocks visit the open camps, 
resting by day on the lagunas, where excellent shooting can 
be obtained at the regular morning and evening flights. 
It breeds in the district, placing the nest under any 
convenient tuft of grass, thistle, &c., in the open camp; the 
structure is lined with down and six to nine eggs are laid. 
The bird sits closely, and usually only rises when one's horse 
almost steps on the nest. 
Thirteen eggs were brought home, collected on Oct. 22nd, 
1909, at Ajo. They measure : axis 2*0 to 33 in., diam. 1*41 
to D55. 
222. Dafila bahamensis. 
Dafila bahamensis Arg. Orn. ii. p. 135. 
Pcecilonetta bahamensis Salvad. Cat. B. xxvii. p. 282. 
a. $ ad. Luiconia, Ajo. Feb. 23, 1909. 
Irides crimson ; bill black, slaty at tip, basal patch red; 
legs and toes ash-coloured. 
223. Mareca sibilatrix. 
Mareca sibilatrix Arg. Orn. ii. p. 135; Salvad. Cat. B. 
xxvii. p. 236. 
a, b. $ ? ad. Los Ynglases, Ajo. Sept. 15-23, 1908. 
c, S a( i. „ „ Jan. 19, 1910. 
Irides dark brown ; bill, upper mandible blue slate- 
coloured, tip next to feathers and lower mandible black ; 
legs and toes blue-grey. 
The January bird is shewing considerable signs of wear 
and is beginning to moult. 
