THE FORMATION AND PLIGHT OP BIRDS. 203 



Watch a swift high up sailing about in a clear 

 blue sky. With hardly a movement of wing, the 

 little black- bodied bird will glide down one 

 current that gives the necessary impulse to 

 ascend by another ; now T with a flutter of wing 

 climbing to a greater height, now with con- 

 tracted wing descending to a lower height, 

 now with outstretched and motionless wings, 

 turning to right, turning to left to catch on its 

 side the wind that gives the impulse that carries 

 it forward like the sails of a ship spread out to 

 catch the wind that blows on its beam. 



One of the most beautiful sights the writer 

 has ever seen was a huge flock of starlings and 

 plovers high up in the air, each species keeping 

 together in dense masses, flying backwards and 

 forwards, ascending and descending, but slowly 

 getting further and further away till they dis- 

 appeared as two tiny specks in the quiet glow of 

 an autumn sun. 



Another time he noticed a dense mass of 

 peewits flying, it seemed, for the pure pleasure 

 of flying, and 'as the birds first turned their backs 

 and then their lighter undersides to view, the sun 

 reflected their different colours with lightning- 

 rapidity in bold relief against a black thunder 

 cloud. 



And then that most wonderful flight of all, the 

 migration flight, when the birds in the fall of the 



