The numbers in brackets ( ) in the text refer to the books or papers mentioned in the list at the end of the volume, which is in no ways an attempt at a full bibliography. I have quoted freely from the works of past and living ornithologists. To these I offer apologies if I have misconstrued their arguments, and acknowledge my indebtedness to those whose observations or writing have given me light. In particular I tender thanks to Mr Wells W. Cooke for his permission to reproduce the maps facing pp. 76, 78, 80. I have found his writings and those of Herr Otto Herman and Mr W. Eagle Clarke especially valuable. Mr Eagle Clarke's long looked-for book on Migration is, as I write, still in the press; had mine been more than a manual I should have hesitated to publish until his had appeared. T. A. COWARD. BOWDON, CHESHIRE, _4 November 1911_. CONTENTS CHAP. PAGE I. MIGRATION OF BIRDS 1 Definition--Variation of migration. II. CAUSE AND ORIGIN OF MIGRATION 13 Direction of passage--The potentiality of flight--Habit of wandering--Memory--Extension of range--Influence of Temperature--Desire for Light--Glacial Epoch--Food Basis--Sexual Impulses--Competition. III. ROUTES 33 Route or Broad Front--Coasting--Fly-lines--Isepipteses --Land-bridges--Coast Lights. IV. THE HEIGHT AND SPEED OF MIGRATION FLIGHT 47 Altitude of Normal Migration--Variation in Speed--Effect of Wind. V. ORIENTATION AND ROUTE FINDING 56 Route Finding--Use of Memory--Eyesight--Errors--Guidance of Young--Beam Winds--Homing of Terns. VI. THE DISTANCES TRAVELLED BY BIRDS 65 The Swallow--Variation in Distances--Marking Birds--Results--Routes of the Golden Plover--Evolution of the Routes. VII. MIGRATION AND WEATHER 83 Knowledge of Approaching Weather--Favourable and Unfavourable Conditions--Importance of Winds--Cyclonic and Anticyclonic Winds--Continental Migration. VIII. THE PERILS OF MIGRATION 104 Contrary Winds--Lighthouses and Lightships--Leeward Drift--Catastrophes. IX. EARLY IDEAS OF MIGRATION 114 Literature--Hibernation--Carriage of Small by Large Birds. X. SUGGESTIONS AND GUESSES 119 Trans-Atlantic Migration--Ship-borne Wanderers --Storm-blown Birds--Casual Wanderers--Swimming and Walking.