210 STUDIES IN BIRD-MIGRATION 



the result of careful observations made during six 

 successive seasons (1906-1911). The earliest date for 

 its appearance is 5th April, and the period during 

 which it is most abundant is the fortnisfht which covers 

 the last week of April and the first week of May. 

 After this, stragglers only appear In small parties, and 

 the latest date on which its passage is recorded is 

 9th June. 



Autumn Passage South and Emigration. — The 

 autumn movements from the summer homes towards 

 the winter retreats follow the same lines of flight along 

 our shores as those already indicated for the spring, 

 save, of course, that they are in a reverse direction. 

 The birds are then more abundant than in the spring, 

 since the ranks of the migrants are recruited by the 

 young birds a few weeks old. It is usually seen in 

 parties of from ten to twenty individuals, but I have 

 seen as many as fifty together at Fair Isle and thirty 

 at St Kilda. These migrants are generally actively 

 engaged in the capture of flies, which are very numerous 

 among the rotting seaweed which fringes the beaches 

 at high-water mark ; they are numerous, too, in the 

 neighbourhood of stations at which fish is exposed for 

 drying, where also dipterous insects abound. 



The etirliest date for the bird's appearance at this 

 season at Fair Isle is 9th August 1909. It becomes 

 more numerous as the month advances, and the move- 

 ments continue in full swing until mid-September. 

 After this the passage, though still in progress, is 

 participated in by fewer individuals, but small numbers 

 are observed annually until mid-October. Odd birds, 

 however, occur in November, and One obtained on the 

 9th of that month, in 1908, was forwarded to me for 



