PART II.— MIGRATION. 

 CHAPTER VII. 



ROUTES OF MIGRATION. 



Difficulty of tracing Routes to British Islands — Definition of a 

 Migration Route — The Gradual EtTects of a Changing Climate 

 on Birds — Impulses to Emigration and Migration — The Turn- 

 stone and the Rose-coloured Pastor — Ancient Breeding Ranges 

 — Inter-polar and Inter-hemisphere Species — Breeding Grounds 

 and Winter Quarters coalescing^ Routes followed by Summer 

 Migrants to British Area — Routes into the South of England — 

 Species following them — -Routes into Ireland — How followed 

 by Birds— Absence of Routes into Scotland via Ireland — Past 

 Physical Changes indicated by Present Routes of Migration — 

 Persistency shown by Birds in following Migration Routes — 

 Across the English and St. Georges Channels and the North 

 Sea — Palmen's "Fly Lines" — The North Sea Routes— Origin 

 of— Effects of Submergence on the Emigration and Migration 

 of Birds — West to East Migration— Water Areas a Check to 

 Emigration — Routes followed by Winter Visitors to and Coast- 

 ing Migrants over the British Islands — The Routes of Migration 

 that are most followed— Inland Continuation of Migration 

 Routes — Difficulty of Tracing — Correlation of Routes with 

 Breeding Grounds. 



It is a somewhat difficult matter to trace the various 

 routes by which migratory birds enter the British 

 Islands, especially in the south. This difficulty is en- 

 tirely due to our want of requisite information. I yield 

 to no one in my readiness to admit the value of the 



