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 
