THE COWBIRDS. 621 



With the results just recorded I felt more than satistied, though so 

 much still remained to be known, and 1 looked forward to the next 

 summer to work out the rich mine ( n which 1 had stumbled by chance. 

 Unhappily, when spriug came around again ill health kept me a prisoner 

 in the city, and finding no improvement in my condition, I eventually 

 left Buenos Ayres at the close of the warm season to try whether 

 change of climate would benetit me. Before leaving, however, I spent 

 a few days at home and saw enough then to satisfy me that my conclu- 

 sions were correct. Most of the birds had finished breeding, but 

 while examining some nests of Annmbius I found one which Bay-wings 

 had tenanted, and which for some reason they had forsaken, leaving 10 

 unincubated eggs. They were all like Bay-wings' eggs, but I have no 

 doubt that 5 of them were eggs of ilL rufoaxillaris. During my rides 

 in the neighborhood I also found two flocks of Bay-wings, each com- 

 posed of several families, and among the young birds I noticed several 

 individuals beginning to assume the purple plumage, like those of the 

 previous autumn. I did not think it necessary to shoot more specimens. 



The question why M. hadius permits M. rufoaxillaris to use its nest, 

 while excluding the allied parasite, M. bonariensis, must be answered 

 by future observers; but before passing from this very interesting 

 group {Molothrns), I wish to make some general remarks on their habits 

 and their anomalous relations to other species. 



It is with a considerable degree of repugnance that we regard the 

 parasitical instincts in birds. The reason it excites such a feeling is 

 nuinifestly because it presents itself to the mind as — to use the words 

 of a naturalist of the last century, who was also a theologian, and 

 believed the Cuckoo had been created with such a habit — "a monstrous 

 outrage on the maternal affection, one of the first great dictates of 

 nature." An outrage, since each creature has been endowed with this 

 all-powerful affection for the preservation of its own, and not another, 

 si)ecies; and here we see it, by a subtle process, an unconscious iniq- 

 uity, turned from its puri)ose, perverted and made subservient to the 

 very opposing agency against which it was intended as a safeguard. 

 The formation of such an instinct seems, indeed, like an unforseen con- 

 tingency in the system of nature, a malady strengthened, if not induced, 

 by the very laws established for the preservation of health, and which 

 the vis medicairix of nature is incai)able of eliminating. Again, the 

 egg of a parasitical si)ecies is generally so much larger, differing also 

 in coloration from the eggs it is placed with, while there is such an 

 unvarying dissimilarity between the young bird and its living or mur- 

 dered foster brothers, that, unreasoning as we know instinct, and 

 especially the maternal instinct, is, we are shocked at so glaring and 

 flagrant an instance of its blind stupidity. 



In the competition for place, the struggle for its existence, said with 

 reason to be most deadly between such species as are most nearly 

 allied, the operations are imperceptible, and the changes are so gradual 



