Open main menu

Page:Ornithological biography, or an account of the habits of the birds of the United States of America, volume 1.djvu/524

This page has been validated.
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 deposited, are all smaller than itself. That which is most frequently favoured 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 return 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.