Paraguay , Bolivia, and Southern Brazil . 105 
This species is nearly as abundant as M. bonariensis in 
the Ajo district, and was the commonest Cow-bird observed 
on the river expedition. 
The nests taken were found in the old nests of Anumbius 
acuticaudatus, and contained eggs both of this species and 
of M. rufoaxillaris, while, judging by the eggs found in the 
nest of Pseudoleistes virescens, the eggs with large spots and 
mottlings are those of M. rufo axillaris, and those with the 
more even markings belong to this species. 
58. Dolichonyx oryzivorus. 
Dolichonyx oryzivorus Scl. Cat. B. xi. p. 331. 
a. ? ad. Alto Paraguay, Bolivia. Oct. 15, 1909. 
Iris hazel; bill, legs, and toes horn-brown. 
59. AgelvEUs thilius. 
Agelceus thilius Scl. Cat. B. xi. p. 343 ; Arg. Orn. i. 
p. 97. 
a, b. S ad. Los Ynglases, Ajo. Sept. 1908. 
Iris dark brown; bill, legs, and toes black. 
c. $ ad. Los Ynglases, Ajo. Dec. 24, 1908. 
d. $ ad. ,, „ Jan. 4, 1909. 
e. S imm. „ „ Feb. 16, 1909. 
f g. S ad. et imm.; h. $ ad. Los Ynglases, Ajo. March 
1909. 
i, k, l. S ad. et imm. ; m. ? ad. Los Ynglases, Ajo. 
April 1909. 
This is another common and resident species in the Ajo 
district, and, as a rule, frequents the vast swamps or 
canadons ; during the winter months it assembles in flocks 
of several hundred individuals. 
The cup-shaped nest is composed of dry grass, and 
is situated in the thick masses of grass in the swamps 
only a foot or so above the level of the ground or water. 
Three eggs appear to form the complete clutch. 
60. Agel^ius ruficapillus. 
Agelceus ruficapillus Scl. Cat. B. xi. p. 347; Arg. Orn. i. 
p. 99 ; Claude Grant, Bull. B.O.C. xxv. p. 114 (1910). 
a. d • Mortero, Paraguay. Aug. 13, 1909. 
