98 BIRDS OF LA PLATA 



filling its crop with air, to use it as a " chamber of 

 resonance*" The note I have described is quickly 

 and invariably followed by a scream, harsh and 

 impetuous, uttered by the female, though both 

 notes always sound as if proceeding from one bird. 

 When on the wing the birds all scream together in 

 concert. 



The food of this species is chiefly minute seeds 

 and tender buds ; they also swallow large cater- 

 pillars and spiders, but do not, like their congeners, 

 eat hard insects* 



I became familiar, even as a small boy, with the 

 habits of the Screaming Cow-bird, and before this 

 species was known to naturalists, but could never 

 find its nest though I sought diligently for it* I could 

 never see the birds collecting materials for a nest, 

 or feeding their grown-up young like other species, 

 and this might have made me suspect that they did 

 not hatch their own eggs ; but it never occurred to 

 me that the bird was parasitical, I suppose because 

 in summer they are always seen in pairs, the male 

 and female being inseparable* Probably this is the 

 only parasitical species in which there is conjugal 

 fidelity* I also noticed that when approached in the 

 breeding-season the pair always displayed great 

 excitement and anxiety, like birds that have a nest, 

 or that have selected a site on which to build one. 

 But year after year the end of the summer would 

 arrive, the birds re-unite in parties of half a dozen, 

 and the mystery remain unsolved* At length, after 

 many years, fortune favoured me, and while ob- 



