126 BIRDS OF LA PLATA 
brought about in this way. But, it may be added, if 
besides the Yellow-breast some one other species 
laying very different eggs (a Zonotrichia or Tyrannus, 
for instance) should also acquire this distinguishing 
habit and eject all eggs unlike its own from its nest, 
the habit in the two or more species would ultimately 
cause the extinction of the parasite. 
It might throw some light on this obscure subject 
to examine, for several successive summers, a large 
number of nests, to ascertain whether the nests of 
the Yellow-breast are often found without any white 
unspotted eggs, or if the same proportional number 
of white (parasitical) eggs are found in the nests of 
the Yellow-breast, Scissor-tail, Song-Sparrow, Pipit, 
and other species. 
PATAGONIAN MARSH-STARLING 
Trupialis militaris 
Brown, variegated with black; superciliaries in front of eye red, 
behind the eye white; throat, middle of neck, and breast scarlet ; 
under wing-coverts white; bend of wing red; length 10 inches. 
Female similar. 
Two species of Trupialis inhabit the southernmost 
part of the Argentine Republic, the present being 
confined to Patagonia and South Chili, while its 
northern representative inhabits the pampas of 
Buenos Ayres and Uruguay. Probably the Colorado 
river, which separates two districts differing in soil 
