This cuckoo is famous for its singular habit of placing its egg in the nest of some other bird, instead of making a nest of its own. The hen bird seems, first of all, to lay her egg on the ground; then, picking it up in her beak, she flies off to look for a suitable nest in which to put it. Having found one, she waits her opportunity, when the occupant is absent, and then slips in the egg and flies away. The owner of the nest, strange to say, hardly ever seems to notice when she comes back that there is a strange egg among her own, although very often it is not in the least like them in color and markings. So before very long a young cuckoo is hatched out, together with her own little ones. Then on the very day of its birth the cuckoo seems to make up its mind that before long there will be no room in the nest for any one but itself, and actually pushes all its little foster brothers and sisters over the side, one after the other! And, strange to say, the mother bird does not seem to mind, but just gives all the food which her own young would have eaten to the cuckoo, and takes the greatest care of it in every way until it is able to fly. The cuckoo family is a large and varied one, with representatives in all parts of the world, and few of them show this extraordinary disposition to impose upon their neighbors, though all are careless home-makers. In the United States we have two kinds of cuckoos, the black-billed and the yellow-billed, which have much the same slim form and plain yet elegant dress as their European cousin, but a different note, uttering a loud rattling cry instead of the soft _cuck-oo_; and both of these make nests, lay eggs in them, and rear their young as faithfully as other birds. The nests, however, are merely loose platforms of twigs set among the branches of some small tree, through which, often, the greenish-blue eggs are distinctly visible. NIGHTJARS The nightjars are another world-wide family, with great similarity in both appearance and habit among its members. All are nocturnal, have big heads, large eyes, and very small beaks, although the mouth opens very wide. They hunt their food by night, resting during the day in shady forests or caves; and like owls they have plumage so plainly brown and gray, and so soft, that their flight is noiseless and almost invisible. The name--which refers to its jarring cry, which is more or less characteristic of the whole family--was given first to the British species, which is often called fern-owl in England. Late in the evening you may often hear it uttering its curious note--"chur-r-r-r-r-r"--which sometimes goes on without any break for three or four minutes.