116 BIRDS OF LA PLATA 
or stalk while singing, and makes a long pause after 
every note or two, as if to make the most of its 
limited repertory. There is in the song one rich full 
note which, to my mind, is unequalled for plaintive 
sweetness, and I am therefore surprised that Azara 
says only of this species that it sings passably well— 
“canta razonablemente.” 
The nest is neatly made of dry grasses, and attached 
to the rushes growing in the water. The eggs are 
four, pointed, and spotted at the larger end with dull 
brown and black on a white ground. 
I wish my dull brains had been able to find some 
shorter, more descriptive English name for this 
species, which of all this group of Troupials, the 
Marsh-birds or Bobolinks of South America, endeared 
itself most to me on account of its grace and lovely 
black and yellow livery, its pretty social habits, and, 
above all, its unforgettable song, or rather that one 
full, beautiful, passionate note on which it ends, 
YELLOW-HEADED MARSH-BIRD 
Agelzus flavus 
Black; head, rump, bend of wing and under surface brilliant 
yellow ; bill and feet black ; length 6.7 inches. Female brown, slightly 
striated ; eyebrows, rump, and under parts yellowish. 
Azara called this bird Cabeza amarilla, or Yellow- 
head, and I retain the name, though it is an unsatis- 
factory one as the bird has so much yellow on its 
