234 



xi\- CONTEyTS 



CHAPTER VIII. 



CONDITIONS OF FLIGHT. 



Routes of Migration, how followed by Birds — Paley's Defi- 

 nition of Instinct — Impulse of ^Migration — Restlessness of 

 Captive Birds — Certain Routes followed by Certain Indi- 

 viduals — How a Route of Migration has been Learnt — 

 Mysterious "Sense of Direction" a Myth — Altitude of 

 Migration Flight — Advantages of a Lofty Course — The 

 Order of Migration — A few Old Birds migrate as Early as 

 the Young — The Daily Time of Migration — Amount of 

 Sociability amongst Birds on Passage — The Perils of 

 Migration ... ... ... 



CHAPTER IX. 



THE SPRING ASPECTS OF MIGRATION IN THE P.RITISH 

 AREA. 



Commencement of Spring ^Migration in the British Islands — 

 Departure of Eastern Migrants — Departure of North- 

 Eastern Migrants — Abnormal Lines of Migration from the 

 British Area — Birds migrating too Early — Arrival of First 

 Spring Migrants from the South — Departure of Winter 

 Visitors to the British Islands — Coasting Migration in 

 Spring — Migration of various Northern Birds — Arrival of 

 Summer Migrants in the British Islands — The Growing 

 Intensity of Spring Migration — Months of Passage of 

 various Species — Gradual Advance northwards of Migrants 

 — Duration of Spring Migration — Vertical Migration in 

 Spring — The various Species performing it — Order of 

 Migration — Table indicating the Spring Migration of Birds 

 across the British Islands ... ... ... ... ... 243 



CHAPTER X. 



'JHE AUTUMN ASPECTS OF MIGRATION IN THE BRITISH 

 AREA. 



Migration more Apparent in Autunm than in Spring— Diffi- 

 culties of Observing the Phenomenon — Commencement of 

 Autunm Migration in the British Islands — Arrival of Birds 

 from the North and North-East — The Species that are the 



