112 



xii CONTENTS. 



Islands — Avifauna of the Bermudas — Avifauna of 

 British Islands — British Local Races — Evidence of 

 Emigration in British Islands — Importance of Emi- 

 gration ... 



CHAPTER VI. 



INTERNAL MIGRATIONS AND LOCAL MOVEMENTS. 



Vertical ]\Iigration — Instances of, in India — Instances of, 

 in Algeria — Not confined to Endemic Species — In- 

 stances among Migratory and Sedentary Species — 

 Vertical Migration among Mountain Species — Simi- 

 larity between Vertical and Latitudinal Migration- 

 Initiating Causes — Migration in the Southern Hemi- 

 sphere — Scarcity of Southern Hemisphere Migrants 

 to Northern Hemisphere — Important bearing on Mi- 

 gration of this Fact — Polar Breeding-Grounds — Law of 

 Northern and Southern Migrations — Reversal of Polar 

 Breeding Areas — Results on jNIigration — Comparative 

 Examination of Northern and Southern Hemisphere 

 Migration — Instances of Northern Migration from 

 Southern Latitudes — IMigrations of various Petrels — 

 Single Breeding of Migrants — Possible undiscovered 

 Antarctic Breeding-Grounds — Migrants not Breeding 

 in Northern Hemisphere — Neutral Zones of Non- ' 

 Breeding Birds — Isolation of Northern Types in 

 Southern Hemisphere — Local Movements of Birds — 

 Winter Migration— Importance of Local Movements 

 in preserving Species ... ... ... ... ••• i35 



CHAPTER VII. 



NOMADIC MIGRATION. 



Nomadic Migration most prevalent in Cold Regions — 

 Resident Birds in the Arctic Regions— The Corvid/e 



