Evolution of migration routes 70 Vertical migration 72 Vagrant migration 73 Perils of migration 75 Storms 75 Aerial obstructions 76 Exhaustion 78 Influence of the weather on migration 80 Problems of migration 81 Banding studies 81 Movements of residents 82 Migration of the white-throated sparrow 84 Migration of the yellow-billed loon 84 Conclusions 85 Appendix I--List of birds mentioned in the text 87 Appendix II--Bird banding 92 Bibliography 94 Index 99 MIGRATION of BIRDS When the birds that have nested in our dooryards and those that have frequented the neighboring woods, hills, and marshes leave us in the fall, the question naturally comes to mind: Where do they go? This, however, is only one small part of the question as we also wonder: Will the same ones return next spring to their former haunts? What dangers will they face on their round-trip flight and while in their winter homes? These and other questions on the migratory habits of most species of Northern Hemisphere birds puzzle all who are interested in them, whether it be the farmer who profits by their tireless warfare against the weed and insect pests of his crops, the bird student who enjoys an abundance and variety of feathered inhabitants about him, or the hunter who wants a continuation from year to year of the sport of wildfowling. Lack of information on the subject may mean the loss of an important resource by unconsciously letting it slip from us, as ignorance might be responsible for inadequate legal protection for such species as might urgently need it. More general knowledge on the subject will aid in the perpetuation of the various migrants, the seasonal habitats of some of which are in grave danger from man's utilization, sometimes unwisely, of the marsh, water and other areas that were formerly homes for birds.