THE CUCKOOS AND THE OUTWITTED COW-BIRD 45 



Even the tiny egg of a butterfly has its ichneu- 

 mon parasite, a microscopic wasp, which lays its 

 own egg within the larger one, which ultimately 

 hatches a wasp instead of the baby caterpillar. 



But who ever heard of anything but good luck 

 falling to the lot of cow-bird or cuckoo, except as 

 its blighting course is occasionally arrested by the 

 outraged human ? They always find a feathered 

 nest. 



In this connection it is interesting to note cer- 

 tain developments in bird life upon the lines of 

 which evolution might work with revolutionary 

 effect. Most of our birds are helpless and gener- 

 ally resigned victims to the cow -bird, but there 

 are indications of occasional effective protest 

 among them. Thus the litcle Maryland yellow- 

 throat, according to various authorities, often 

 ousts the intruded egg, and its broken remains 

 are also occasionally seen on the ground beneath 

 the nests of the cat-bird and the oriole. The red- 

 eyed vireo, on the other hand, though having ap- 

 parently an easier task than the latter, in the 

 lesser depth of her pensile nest, commonly aban- 

 dons it altogether to the unwelcome speckled 

 ovum always, I believe, if the cow -bird has an- 

 ticipated her own first egg. 



But we have a more remarkable example of 



