THE COW-PEN-BIRD. 19 



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 occa- 

 sions, 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 return south- 

 ward. 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. When the female 

 returns, and finds in her nest an egg which she immediately perceives to be 

 different from her own, she leaves the nest, and perches on a branch near it, 

 returns and retires several times in succession, flies off, calling loudly for her 

 mate, who soon makes his appearance, manifesting great anxiety at the 

 distress of his spouse. They visit the nest together, retire from it, and con- 

 tinue chattering for a considerable time. Nevertheless, the obnoxious egg 

 retains its position, the bird continues to deposit its eggs, and incubation 

 takes place as usual. The egg of the Cow-bird is of a regular oval form, 

 pale greyish-blue, sprinkled with umber-brown dots and short streaks, which 

 are more numerous at the larger end. 



Incubation has been continued for nearly a fortnight, and the young Cow- 

 bird bursts the shell. Another remarkable occurrence now takes place. The 

 eggs of the foster-bird are yet unhatched, and soon after disappear. In every 

 case the Cow-bird's egg is the first hatched, and herein also is manifested 

 the wisdom of Nature; for the parent-birds finding a helpless object, for 

 whose subsistence it behoves them to provide, fly off to procure food for it. 

 The other eggs are thus neglected, and the chicks which they contain neces- 

 sarily perish. Birds have probably the means of knowing an addle egg, for, 



