It has been put forward as a serious objection to many arguments that migration, instead of being advantageous to birds, is a danger to the race; that the perils of the journey are greater than those occasioned by more sedentary habits. It has even been suggested that migration is a habit specially created to thin down the surplus bird population. Dr W. K. Brooks, however, puts this idea, which is not entirely devoid of truths, in rather a different way. "Adaptations of nature are primarily for the good of the species--beneficial to individuals only so far as these individuals are essential to the welfare of the species" (9). The destruction of overabundant young, the thinning down of superfluous numbers, may be an economic advantage. It is one thing to say that migration has been caused to kill off a surplus, and another to show that, once a habit has been originated and become an advantage, it will be conducive to a greater prolificness, and that the natural sequence of an increased birthrate, when food supply and other conditions remain unchanged, must be an increased mortality. Thus the perils of migration may become a boon to the species. The theories of C. L. Brehm (7) and Marek that birds are living barometers, foretelling by intuition the changes of barometric pressure, may be dismissed as purely speculative. That birds begin their journeys during particular barometric conditions is certain, but what they know of forth-coming weather conditions is guess-work. * * * * * CHAPTER III ROUTES The migrating bird, when passing between the breeding home and the winter quarters, travels by what is termed its Route. The definition of the route has caused more controversy than perhaps any other incident of migration; the chief point at issue is whether the bird uses a particular high road, along which all its fellows from the same area travel, or if all birds move in what has been called a "Broad Front." Ornithologists have been, and to some extent still are, divided into two camps, one upholding defined routes and the other the extended or broad front movement.