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 lay 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 



