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 



