“Precisely. Now see by what wonderful planning the strange egg comes to be adopted by another mother. Bear in mind that the cuckoo lives exclusively on insects. The young cuckoo must have caterpillars. Where will food of this sort be found if not in the nests of birds that feed on insects, as for instance warblers, redbreasts, tomtits, nightingales, stonechats, wagtails, and others? It is to just these nests that the cuckoo goes. Sometimes it may chance to lay its eggs in the nests of birds that live on seeds, such as linnets, bullfinches, greenfinches, or yellow-hammers; but even then the choice is wise; for if the foster-parents are eaters of seeds they bring up their young on worms, which are easier to digest, and so the little cuckoo finds in these nests food suited to its needs. But the cuckoo’s eggs are never laid in the nests of quails, partridges, or other species whose young are granivorous from the beginning. In a brood whose habitual diet was not theirs the changelings would surely die of hunger.” “But how,” asked Jules, “does the cuckoo know what nests to choose and what ones not to choose, when it lays its eggs?” “If it knew why it laid its eggs where it does, I should have to admit that the cuckoo’s sagacity surpassed man’s; but it does not know at all the reason for its choice. A wise Providence has arranged everything for the bird. The egg—which, judged by the cuckoo’s size, should be as large as a pigeon’s or a turtle-dove’s—is hardly as big as a sparrow’s, so that it can easily find a place in the warbler’s or even the wren’s tiny nest without arousing the adoptive mother’s suspicions. Moreover, this egg is variable in its color, as if the better to harmonize with the coloring of those with which it will be incubated, whether in this or that or the other nest. Sometimes the cuckoo’s egg is ash-colored, at other times red, green, or pale blue. It may closely resemble the sparrow’s eggs, or it may be mottled with spots of smaller or larger size, in lesser or greater numbers; or, again, it may be marbled with black streaks. But, despite these variations, it is always easy to see the difference between the cuckoo’s egg and the others in a nest. If one of the eggs is found to differ from the others in shape and color, that one certainly came from the cuckoo. By that sign alone I recognized the egg we have here from the warbler’s nest.” “The other five,” Jules declared, “are as like one another as so many drops of water; but the sixth, which you have there, is very different.” “And that is why I am sure it belongs to the cuckoo,” replied his uncle. “The cuckoo seems to me,” said Louis, “very large to be able to get into such a small nest as the warbler’s, the redbreast’s, or the nightingale’s, so as to lay its egg there.”