CHAPTER IV. 



ROUTES OF MIGRATION. 



Intricate Nature of Fly-lines — Sea Routes of Migration — 

 Migration over the Azores — Migration at the Bermudas — 

 Its Abnormal Character — Migration over Seas by means of 

 Islands — Migration over the Mediterranean — The North 

 Sea Routes — Rarity of Migration to New Zealand — 

 Migration Routes Continuous — x\ntarctic Migration — 

 Geological Changes in Antarctic Regions — Coast Routes of 

 Migration — Their Continuity — How followed by Migrants 

 — Ancient Routes of Migration — Instances of Species still 

 following them — Submerged Land Areas — Coast Migrants 

 — Valley Routes of Migration — Cross Valley Routes — ■ 

 Valley Routes to India — Abnormal Migrants to that 

 Country — American River Routes — River Valleys ex- 

 ceptionally favourable to Migrants — Mountain Routes of 



■ Migration — Mountain Migrants — Migration through Moun- 

 tain Passes — Varied Character of Migration Routes — 

 Routes of Migration indicating Emigration. 



The next portion of our subject with which it 

 becomes necessary to deal, embraces the various 

 Routes that are followed by migratory birds. These 

 highways of migration are both numerous and well 

 recognized ; many of them are extremely com- 

 plicated. Probably the fly-line of no two species is 

 exactly the same ; and the variety of route seems 

 almost as excessive among individuals as among 

 species. Each appears to follow a route which 



