496 COW-PEN BIRD. 



suitable repository for her egg, she waits for a proper opportunity, drops 

 it, flies off", and returns in exultation to her companions. 



The birds in whose nests the eggs of the Cow Bunting are thus de- 

 posited, are all smaller than itself. That which is most frequently fa- 

 voured with the unwelcome gift is the Maryland Yellow-throat. The 

 other species in which I have found the egg of the Cow Bird are the 

 Chipping Sparrow, the Blue Bird, the Yellow Bird, several Fly-catchers, 

 especially the Blue-grey and the White-eyed, and the Golden-crowned 

 Thrush. The nests of these birds are very different in form, size and 

 materials, as well as in position, some being placed high on trees, others 

 in low bushes, and that of the Thrush on the ground. 



It is also a very remarkable circumstance, that although the Cow- 

 Bird is larger than the species in the nests of which it deposits its eggs, 

 the eggs themselves are not much superior in size to those of their 

 intended foster-parents. This is equally the case with the European 

 Cuckoo, which selects, for the purpose of depositing its egg, the nest of 

 the Titlark, Hedge-Sparrow, or some other small bird. And here, as in 

 so many other cases, may we observe the adaptation of means to ends 

 which nature has so admirably made. The egg of the Cuckoo, in fact, 

 is not so large as that of the Skylark, a bird which, to the other, hardly 

 bears the proportion of one to six. The intention here has not been by 

 a similarity in size and colouring, to deceive the bird in whose nest the 

 egg is placed, for, on all occasions, the individuals on which the gift 

 have been bestowed, receive it unwillingly, and, in fact, manifest great 

 alarm and resentment. On the contrary, the object has been to secure 

 the development of the embryo, by adapting the size of the egg to the 

 capability of imparting heat to it. 



Should the Cow-Bird deposit its egg in a nest newly finished, and as 

 yet empty, the owners of the nest not unfrequently desert it ; but, when 

 they have already deposited one or more eggs, they generally continue 

 their attachment to it. There is reason for believing, however, that, on 

 all occasions, they are aware of the intrusion that has been effected. 



The Cow-Bird never deposits more than one egg in a nest, although 

 it is probable it thus leaves several in different nests, especially when we 

 consider the vast numbers of the species that are to be seen on their re- 

 turn southward. It does not make a forcible entrance, but watches its 

 opportunity, and when it finds the nest deserted by its guardians, slips 

 to it like one bent on the accomplishment of some discreditable project. 



