CONTENTS xi 



Pelicans, Darters, and Frigate Birds — The 

 Screamers, Flamingoes, Swans, Geese, Ducks, 

 and Mergansers— The Finfoots and Rails— The 

 Cranes, Trumpeters, Screamers, and Sun Bitterns — 

 The Game Birds— The Sand-Grouse — The Pigeons 

 —The Plovers and Snipes, &c.— The Gulls, Terns, 

 Skuas— The Auks — The Birds of Prey — The 

 Coraciiformes— The Parrots— The Cuckoos and 

 Plantain-Eaters — The Passeriformes or Perching 

 Birds 



PAGES 



103-142 



CHAPTER IV 



THEIR MEANS OF DISPERSAL AND MIGRATIONS 



The dispersal of birds— Fortuitous dispersal— Ancient 

 land-surfaces— Polar dispersal— Equatorial disper- 

 sal—The law of dispersal— Obstacles to dispersal 

 — Discontinuous areas of dispersal— Influence 

 of climate upon species — Species increasing 

 their range during present time— The migration 

 of birds — Misconceptions concerning migration — 

 Transmutation and Hibernation — Migration and 

 Instinct — Migration not universal in certain species 

 — The Cause of Migration — Migration due to range 

 expansion or colonisation — Cause of migration in 

 autumn— Length of journey variable— The Philo- 

 sophy of Migration — The wings of migrants — 

 Moulting of migrants— Course of autumn migra- 

 tion — How birds find their way on migration — 

 Migration across seas— General aspects of migra- 

 tion — Duration of migration — The speed of migra- 

 tion flight— The height at which migrating birds 

 fly — The perils of migration — Lost birds at 

 lighthouses — Various kinds of migration — Vertical 

 migration— Local movements of birds— Nomadic 

 migration — Irruptic movements . . . 143-177 



