Note 8 — Chapter VIII · THE CORDILLERA OF THE ANDES

We now know far more about the migrations of birds than was known only a few decades ago. We are able to locate many of them during the various seasons of the year, and are quite certain that they never, as an ingenious writer of the early seventeenth century maintained, spend the winter in the moon, where they have no occasion for food; but we have yet much to learn regarding the causes of their periodic migrations, and the nature of that instinct that enables them to pass, with unerring precision, from the arctic to the antarctic regions, and from the Old World to the New. We are accumulating daily new facts regarding the distant flights of the birds of passage, but, notwithstanding the many theories, some of them more fantastic than scientific, that have been advanced to explain the cause of the migrations of birds; why such migrations were undertaken in the beginning, why they are still continued, and how birds are able to find their way, during their marvelous flights from the arctic to the antarctic—we are still in the dark about many questions connected with those mysterious migrations, which have excited the interest of even the most casual observer since the prophet Jeremiah wrote: “The stork in the heaven knoweth her appointed time; and the turtle and the crane, and the swallows observe the time of their coming.”8