OUR RARER BIRDS 



lofty mountain passes ; whilst others wing their way through 

 the very loftiest air. Many of these flight routes, or "fly- 

 lines," are extremely complicated, and the road taken by one 

 species is often crossed at right angles by that taken by another. 

 Many species seem to follow the direction of ancient coast- 

 lines, now lying buried under the ocean ; and this fact may 

 account for so many birds crossing the North Sea to this 

 country, and then heading southwards across the English 

 Channel again. Vast numbers of birds pass our coasts in 

 their great northern or southern journey every season ; and 

 many of our own birds fly direct south till they reach the 

 English Channel, and then pass along the coast and downs from 

 Lands End to Dover before they cross the sea and follow the 

 continental coast-line to Africa. Most birds perform their 

 migrations, especially in spring, very quickly ; and I am of 

 opinion that they fly at enormous altitudes, far beyond the 

 range of human vision, through the stratum of rarefied air 

 which makes their progress easy, and also assists them 

 materially in their topography. 



The migration of birds is most marked in autumn. In 

 spring they come singly or in little parties, and pass as 

 rapidly as possible from place to place ; but in autumn many 

 species gather into enormous flocks for the purpose. "Who 

 has not seen the Swallows gathered in fluttering thousands 

 on the late September days, when the autumnal tints are 

 creeping over the trees and hedges ? Who has not watched 

 the vast flocks of wading birds gathered together for the 

 purpose of journeying in company ? How many times do we 

 pause to admire a little party of Pipits, or Chats, restlessly 

 flying southwards ; or a company of Goldcrests all eagerly 

 speeding away ? Many birds join flocks of a different species 

 to migrate with them ; others always fly in pairs ; others, 

 again, in family groups. Some birds separate into sexes to 

 migrate, the males being the first to arrive in spring and 



