298 Zoological Collections, Vertebrata. 



engaged in constructing their nests. Should she not from this position dis- 

 cover a nest, she moves off, and flies from tree to tree, until at length, having 

 found a 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 deposited, 

 ^re all smaller than itself. That which is most frequently favoured with the 

 Upwelcome gift is the Maryland yellow-throat. The other species in which 

 I have found the e^g of the cow bird are the chipping sparrow, the blue 

 tird, 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 e^g, the nest of the titlark, hedge-sparrow, 

 pr 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 sky- 

 lark, 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 whom the gift has 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. 



Shoujd 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 dis- 

 tress 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 

 fopd for it. The other eggs are thus neglected, and the chicks which they 

 contain necessarily perish. Birds have probably the means of knowing an 

 addle egg, for, when, any such remain aftei; the hatching of the others, they 



