BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 381 



on June 29, 1920, the yelloAv-shoiildered blackbird was fairly common 

 in marshy spots near the Rio de la Plata in small flocks or scattered 

 singly throiif^h the rushes. On July 15 a flock of a dozen was noted 

 near a small lagoon at Las Palmas, Chaco, the farthest north at 

 which the birds were recorded. On October 21, near Dolores, Buenos 

 Aires, they were in pairs and males were singing. Near Lavalle 

 from October 23 to NoA'ember 15 they were common in the rush 

 grown cahadones. AVhere shrubs or low trees offered perches, the 

 males rested in them, though elsewhere they were content to cling 

 to the side of a reed. 



Near General Roca, Rio Negro, from November 23 to December 

 3, a few were recorded mainly in irrigated alfalfa fields. At Car- 

 hue, Buenos Aires, a pair was seen in a small marsh from December 



15 to 18. On January 16, 1921, birds in molt were noted along tb'^ 

 Arroyo Carrasco, east of Montevideo. At San Vicente, Uruguay, 

 flocks containing grown young were seen January 31, and at Lazcano, 

 Uruguay, small numbers were found in marshes grown with saw 

 grass from February 5 to 9. At Tunuj^an, ]\Iendoza, from ]March 

 22 to 28, they gathered with cowbirds in cornfields bordering the 

 cienagas where they did considerable damage to corn still in the 

 milk. There was a small but regular evening flight here to some roost 

 in the swamps south of town. 



AGELAIUS CYANOPUS Vieillot 



Agelaius cyanopus Vieillot, Nouv. Diet. Hist. Nat., vol. 34, 1819, p. 552. 

 ( Paraguay. ) 



The form here under discussion was fairly common in the Chaco, 

 but was not seen elsewhere. It was noted at Las Palmas, Chaco, 

 July 22 to 31, 1920 (adult females, July 22 and 28) ; Riacho Pilaga, 

 Formosa, August 9 to IT (immature male and female, August IG) : 

 and Kilometer 80, west of Puerto Pinasco, Paraguay, September 10 

 (male). The wholly black adult males of this Agelaius were so 

 wary that none in that plumage were taken. A male shot August 



16 in color is like the adult female but has a larger bill and longer 

 wing. The immature female is duller below than the adult of the 

 same sex. A male shot September 10 is in molt into adult feather as 

 black is appearing on the head and sides of the breast. 



These blackbirds were found in marshy localities, near lagoons, 

 or about cornfields or other small cultivated tracts on low ground. 

 It was usual to see them resting on rush stems or walking about on 

 masses of vegetation that floated on shallow water. They were 

 frequently rather Avild, and when startled flew out in disorder with 

 undulating flight. Among growths of weeds on the ground they 

 walked about rapidly, clambering over considerable obstructions. 

 54207—26 25 



