Page:Popular Science Monthly Volume 30.djvu/629

Rh enough in its every-day life, acorns. One of the most remarkable instances of avian providence is that related by Saussure, of the Mexican Colaptes. The sides of the extinct crater of Pizarro, in Mexico, are covered during the winter months with the dried-up hollow stalks of the last year's agave-flowers, over which a yucca-tree here and there casts a scanty shadow. Hither, at the time of the ripening of the acorns, come large flocks of the birds with acorns, which they have brought from a great distance, for no oak-tree grows within many miles of the spot. Beginning at the bottom, they bore with their deft bills a succession of holes, at short distances apart, in the hollow agave-stems, and through them deposit their acorns in the interior cavity. The acorns look, when the magazine is filled, laid one after another, like the beads of a rosary. When the time of scarcity arrives, these insect-eating birds hasten to their store-houses, extract the acorns from them, fly with them to the yucca-trees, and, boring in the bark of them holes large enough to hold the acorn, as an egg-cup holds an egg, break open the fruit and eat it in comfort. Saussure avers that the acorns in question are sound, and free from worms.

Other birds, not looking so far into the future, provide only for temporary wants. A species of owl, according to Naumann, feeling the approach of a storm, lay up a stock of mice to last them through the nights when they will be unable to hunt. When the red-backed shrike has caught more than its appetite demands, it spits the surplus—young birds, frogs, and larvæ—on thorns; whence it has been called the thorn-turner, or, because the people believe that the number of its victims is always nine, the nine-killer. Curiously enough, a relative of this shrike, the Collurio Smithii, of Africa, employs, to accomplish a similar object, the more difficult method of slipping one end of a plant-fiber around the victim's neck, and hanging it by the other end to a bush, thereby giving its store-room a kind of resemblance to a gallows-yard. Not only are these lesser special peculiarities, these side-features of the bird's habits, as we might call them, determined by the kind of food and the method that has to be employed to obtain it, but more important and fundamental features of its life, its migrations, its distribution, and many of the motives of its propagation-history, can be traced back to them. The origin of the migratory instinct has usually been sought in climatic causes, and in the desire to avoid the cold and hardships of northern winters. This is an error. The little titmice and modest wrens, which are able to find the most carefully hidden larva in its winter-quarters, and can discover the most minute insect-egg, and which will not disdain a berry or a seed, stay with us through ice and snow; but the larger and stronger cuckoo remains in the north only while insect-life is at its height, and starts early on its southward journey. The great shrike is a permanent resident in Europe, going away only rarely, in case of dire extremity, but its three indigenous relatives are real birds of passage,