ARGENTINE COW-BIRD 75 
cannot find one to match with them, it is impossible 
not to believe that the eggs found together, and 
possessing a family likeness, were laid by the same 
bird. 
5. Several females often Jay in one nest, so that 
the number of eggs in it frequently makes incubation 
impossible. One December I collected ten nests of 
the Scissor-tail (Milvulus tyrannus) from my trees ; 
they contained a total of forty-seven eggs, twelve of 
the Scissor-tails and thirty-five of the Cow-birds. It 
is worthy of remark that the Milvulus breeds in 
October or early in November, rearing only one 
brood ; so that these ten nests found late in Decem- 
ber were of birds that had lost their first nests. 
Probably three-fourths of the lost nests of Milvulus 
are abandoned in consequence of the confusion 
caused in them by the Cow-birds. 
6. The Cow-birds, male and female, destroy many 
of the eggs in the nests they visit, by pecking holes 
in the shells, breaking, devouring, and stealing them. 
This is the most destructive habit of the bird, and is 
probably possessed by individuals in different degrees. 
I have often carefully examined all the parasitical 
eggs in a nest, and after three or four days found that 
these eggs had disappeared, others, newly laid, being 
in their places. I have seen the female Cow-bird 
strike her beak into an egg and fly away with it; 
and I have often watched the male bird perched 
close by while the female was on the nest, and when 
she quitted it have seen him drop down and begin 
pecking holes in the eggs. In some nests found full 
