brings him back, then we have the nest and a small collection of materials near it, which the male, having once begun, would be likely to add to to a certain extent, never getting it quite out of his mind, so to speak. His occasional hesitation between the two would be quite natural, as natural, I think, as most other hesitations either in man or beasts. It is not difficult, then, to imagine the inchoate nest being put to some other purpose, or even that it might be either so put, or become another nest, in the case of one and the same bird or pair of birds; or that some birds of a species, till the habit had become fixed in one or another direction, might be more prone to do the one thing, and some the other. Thus there would be a fluctuating and personal element—something, I think, should be allowed for the personality of each individual creature. Of course, if such an explanation would account in any degree for a superfluity of nests, or for uncompleted nests being put to some other purpose in the case of Grebes, it would do so to the same extent in the case of other birds; and here we come to the one or more extra nests—usually called "cock-nests"—built by Wrens, and the conflict of evidence or opinion as to whether these extra ones are or are not put to any special purpose. But it is not only Wrens—or, as we have now seen, Grebes—that abandon the nest they have been building, and build another. Blackbirds—and here it is the hen only that builds, though closely attended on by the male—are liable to do the same; for I watched a building pair most closely this spring, and, when the nest was almost finished, it was abandoned—quite capriciously, as it appeared to me—and another commenced not far from it. For this reason, and from what we know in regard to the Wren, I do not think the destruction of the original nest was the cause of these Grebes building a third one as well as a second. I attribute it to unsteadiness, or what I have called wavering of the instinct—not meaning by this to wrap up ignorance in a phrase, but rather to imply that no specially induced cause need be assumed. As nature can thus act in the female, one might expect her to do so more often, and in a greater degree, in the male, when he is also the builder.
Before leaving this subject I will just hint the possibility—for here I can do no more—of abandoned nests being the origin of
