ARGENTINE COW-BIRD 71 



deep violaceous purple, the wings and tail being 

 dark metallic green ; but seen at a distance or in 

 the shade the bird looks black. The female is inferior 

 in size and has a dull mouse-coloured plumage, and 

 black beak and legs. The males are much more 

 numerous than the females. Azara says that nine 

 birds in ten are males ; but I am not sure that the 

 disparity is so great as that. It seems strange and 

 contrary to Nature's usual rule that the smaller, 

 shyer, inconspicuous individuals should be in such 

 a minority ; but the reason is perhaps that the male 

 eggs of the Cow-bird are harder-shelled than the 

 female eggs, and escape destruction oftener, when the 

 parent bird exercises its disorderly and destructive 

 habit of pecking holes in all the eggs it finds in the 

 nests into which it intrudes. 



The Cow-birds are sociable to a greater degree 

 than most species, their companies not breaking up 

 during the laying-season ; for, as they are parasitical, 

 the female merely steals away to drop her egg in any 

 nest she can find, after which she returns to the 

 flock. They feed on the ground, where, in their 

 movements and in the habit the male has of craning 

 out its neck when disturbed, they resemble Starlings. 

 The male has also a curious habit of carrying his 

 tail raised vertically while feeding. They follow the 

 domestic cattle about the pastures, and frequently a 

 dozen or more birds may be seen perched along the 

 back of a cow or horse. When the animal is grazing 

 they group themselves close to its mouth, like chickens 

 round a hen when she scratches up the ground, eager 



