380 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



recognition of two races under this species as I have done here. The 

 earliest name apparent for the eastern race is Agelaius chrysopterus 

 Vieillot from the reference cited above. The male of Vieillot's de- 

 scription is a hopeless composite drawn apparently from Agelaius 

 xantho7nus of Porto Rico, and whatever species of Icterus is indi- 

 cated by Latham's Oriolus cayanensis. The female, however, is 

 taken from Azara's account of the Tordo negro cohijas amanllos 

 and refers to the present bird. The name may thus be identified 

 definitely with the eastern form of the yellow-shouldered blackbird. 



An adult male taken at Berazategui, Buenos Aires, on June 29, 

 1920, is in full black plumage save for a few faint, paler margins 

 that remain on the lower breast, abdomen, and lower tail coverts 

 (where they are most pronounced) and on the dorsal surface. A 

 pair in breeding plumage, somewhat worn, were taken at Lavalle, 

 Buenos Aires, November 6 (female) and November 15 (male). At 

 the Laguna Castillos, near San Vicente, Uruguay, I killed a pair in 

 very worn breeding plumage and an immature female not quite 

 fully grown. The adult female is very dark, and both of the older 

 birds are smaller than others I have seen, as the wing in the male 

 measures 80 mm. and in the female 75.4 mm., a condition due per- 

 haps in part to wear. The juvenile female is dark in tone and much 

 browner than others slightly older from other regions. At Tunuyan, 

 Mendoza, on March 23 I secured an adult male, a female of equal 

 age, and an immature female. The male has just completed the post- 

 nuptial molt and has the black obscured in a peculiar way. The 

 crown is bone brown with a central streak of deep olive buff and a 

 superciliary streak of pale olive buff. The hind neck is darker than 

 buffy brown, the back feathers are margined with deep olive buff 

 and natal brown, the greater and median wing coveyts tipped with 

 pale olive buff, and' the feathers of rump and upper tail coverts 

 bordered with deep olive buff. The entire undersurface has the 

 feathers margined with pale olive buff. These lighter markings are 

 lost through wear, so that by spring the bird is black save for the 

 yellow shoulders. Pale markings persist on the under tail coverts 

 longer than elsewhere. 



The adult female from Tunuyan has about completed the body 

 molt, but has all of the rectrices and a few wing feathers growing in 

 anew. Females from Mendoza are distinctly paler than birds from 

 Buenos Aires, and it is probable that they represent a pale form 

 with a range covering marshes in the arid western regions of Ar- 

 gentina. Present material is not sufficient to demonstrate this satis- 

 factorily. 



The yellow-shouldered blackbird is an inhabitant of rush-grown 

 fresh-water marshes, though ranging near the coast where salt water 

 is tempered by springs or streams. At Berazategui, Buenos Aires, 



