MARSH-BIRD 115 



YELLOW-SHOULDERED MARSH-BIRD 



Agelxus thilius 



Black ; lesser upper and under wing-coverts yellow ; bill and feet 

 black ; length 5.5 inches. Female pale brown, striated with black ; 

 eye-mark white ; paler beneath ; smaller. 



THIS bird is abundant everywhere on the pampas, 

 and does not migrate, but inhabits marshy situations 

 in summer, building its nest amongst the rushes, 

 and in winter ranges over the country. The male is 

 entirely of an intense black, except the shoulders, 

 which are pure yellow ; the female is dull grey with 

 fuscous markings, and, as was long ago remarked 

 by Azara, the grey-plumaged are very much more 

 numerous than the black individuals. The young 

 birds are like the females, and possibly do not acquire 

 the full black plumage until the second year, which 

 would account for the great number of grey birds. 



These birds are extremely sociable, being seen in 

 flocks all the year round, even during the breeding- 

 season ; in winter a great many males separate them- 

 selves from the females, and are found associating 

 together in flocks of from thirty to forty individuals. 



They feed on the ground, keeping to the moist 

 borders of marshes during summer ; they avoid 

 woods, but occasionally alight on trees, where they 

 all sing in concert. The song, when an individual is 

 heard singing alone, is, though limited in its range, 

 very sweet, some of the notes being remarkable for 

 their purity and expression. The bird sits on a rush 



