Transcriber's Note Emphasized text is denoted by =Bold= and _Italics_. MIGRATION OF BIRDS [Illustration] Circular 16. Revised Edition - 1979 FISH & WILDLIFE SERVICE / UNITED STATES DEPARTMENT OF THE INTERIOR MIGRATION OF BIRDS By Frederick C. Lincoln Revised By Steven R. Peterson Associate Editor Peter A. Anastasi Illustrated By Bob Hines [Illustration] Circular 16. Revised Edition - 1979 FISH & WILDLIFE SERVICE / UNITED STATES DEPARTMENT OF THE INTERIOR TABLE OF CONTENTS Page PREFACE 1 INTRODUCTION 2 THE HISTORY AND SCOPE OF MIGRATION 4 TECHNIQUES FOR STUDYING MIGRATION 7 Direct Observation 7 Aural 8 Preserved Specimens 8 Marking 8 Bands, Collars, Streamers 8 Radio Tracking 10 Radar Observation 10 Laboratory 11 Orientation and Navigation 11 Physiology of Migration 11 ADVANTAGES OF MIGRATION 13 STIMULUS FOR MIGRATION 15 WHEN BIRDS MIGRATE 17 Time of Year 17 Time of Day 20 SPEED OF FLIGHT AND MIGRATION 25 ALTITUDE OF FLIGHT AND MIGRATION 32 SEGREGATION DURING MIGRATION 35 By Individuals or Groups of Species 35 By Age 36 By Sex 38 By Kinds of Flocks 40 WHERE BIRDS MIGRATE 41 Migration by Populations Within Species 41 Fall Flights Not Far South of Breeding Range 42 Long Distance Migration 44 ORIENTATION AND NAVIGATION 47 INFLUENCE OF WEATHER 51 INFLUENCE OF TOPOGRAPHY 56 PERILS OF MIGRATION 58 Storms 58 Aerial Obstructions 58 Exhaustion 59