74 THE BIOLOGY OF THE SEASONS 



that somehow make their way across the Atlantic. Thus 

 the Kildeer Plover, a distinctively North American bird, 

 was shot at Peterhead in 1868, and has been recorded since. 

 The occurrence of these " casuals " varies in interest ; in 

 some cases the occurrence is so rare that we may almost 

 call it a curiosity ; in other cases it is repeated year after 

 year, and may indicate an extension of range. 



(4) Another general fact admitted by all is that the 

 migratory movements are marked by a high degree of 

 regularity. Whatever it is, migration is not a haphazard 

 business. The same kinds of birds return to the same part 

 of the country about the same time and leave about the 

 same time. The puffin is a good instance of punctuality 

 in arrival, the swift shows the same virtue in its departing. 

 There is some evidence to show that the same pair of birds 

 may return in successive Springs to the same nesting-place, 

 but the only way of making sure of this is to mark the birds. 

 This has been done in the case of house-martin and stork. 

 We can personally vouch for an interesting fact brought 

 out in the course of a Bird-Migration Inquiry now in 

 progress, that a swallow ringed in 1909 came back to the 

 same farm in 1910. 



While some migration is always going on, the greater 

 movements are to be seen, as every one knows, in Spring and 

 Autumn. In Spring we look for the return of our singing- 

 birds ; in Autumn they say good-bye again. But the turn 

 of the tide northwards must be put as early as February, 

 when we hear the honk-honk of the wild geese as they make 

 for the north, and see their impressive flying phalanx ; and 

 the turn of the tide southwards must be put as early as mid 

 June when the adult cuckoos begin to get restless, and fly off, 

 leaving their young ones to the care of their duped foster- 

 parents. At present, however, we wish simply to em- 

 phasise the fundamental fact of orderliness of movement 



