io6 THE BOOK OF NATURE STUDY 



Though undoubtedly the problems of migration are such as 

 can at all times be profitably discussed, yet this is a theme which, 

 just because of its many difficulties, is best attacked when 

 migratory movements are actually taking place, as in the 

 months of March, April and May, and again in August, Sep- 

 tember and October, when the greatest activity is being dis- 

 played. 



The earlier months just enumerated are marked by the depar- 

 ture of birds which have wintered with us for their more northern 

 breeding quarters ; and the arrival of the species which will spend 

 the summer here. During the autumn months this order of coming 

 and going is reversed. 



But these movements must be carefully sought for, especially 

 by those who do not have the good fortune to live near the sea 

 and on the lines of migration. The dwellers inland rarely see 

 more evidence of these arrivals and departures than is afforded by 

 stragglers. On certain parts of the coast, however, especially in the 

 east and south coasts during the autumn, larks, crows and other 

 birds may be observed landing, tired and hungry, in continuous 

 streams, often for days on end ; while the departure of the 

 swallows may similarly be watched in Cornwall. Since, however, 

 they take their leave in the darkness of the night, the actual 

 departure cannot be witnessed, but for days beforehand these 

 birds collect in great bands. 



The most favourable places for the study of actual migration are 

 lighthouses. Here, especially on stormy nights during the autumn, 

 immigrating birds, such as larks, thrushes and starlings, are en- 

 countered in thousands. The poor birds, dazzled by the light, 

 fly round and round the lantern for hours, beating their wings 

 against the glass ; thousands fall to the rocks below, and thousands 

 more into the sea, so that the mortality in a single night may 

 reach an appalling total. During this time, too, hosts of plovers of 

 various kinds wheel round and round, rending the air with their 

 cries, and apparently unable to resist the fascination of the light. 

 Even in London on dark nights the cries of migrating bands of 

 plovers passing over the city may plainly be heard. 



As a rule, birds fly high during migration. But should this 

 take place during a gale they will fly so low that they barely top 



