Migration 



A little thought will show that birds, in the main, 

 travel north in their search for nesting-places and south in 

 their search for food, but it is interesting to note too that 

 migration usually begins some time before the food supply 

 fails. Swifts leave us in July and August, when insect life 

 is at its height. It is probably not cold, as some assert, but 

 the intuition that their food supply will soon fail that drives 

 our migrants south in winter. During the breeding season, 

 family cares compel migrants to limit themselves to a 

 definite district ; but in their winter haunts, free from all 

 cares, many of these migrants are nomadic, as witness the 

 wanderings of flocks of redwings and field-fares over this 

 country in winter. Then, again, certain birds, the snow 

 bunting and shore lark to wit, have been termed gipsy 

 migrants, for the reason that they wander southward only 

 so far as frost and snow compel them they are always 

 trying to go north. 



Observation, too, has shown that many migrants have 

 certain favoured spots in this country which they visit 

 from year to year during their pilgrimage ; thus certain 

 migratory sandpipers regularly visit the lower reaches of 

 the Mersey every autumn. This " regularity of appearance 

 suggests habit and memory" rather than a haphazard 

 discovery of a favourable food supply. 



It has been asserted that family instincts are at the root 

 of bird migration. That this may have been so originally is 

 possible, but incapable of proof, and there are other theories 

 which we shall mention later. Were family affairs the crux 

 of the matter, there would not be such a large proportion 

 of immature migrants. Moreover, these inexperienced 

 birds are often the first to make the long journey from 

 their southern feeding-grounds. With such vast hordes of 

 birds arriving at and departing from our shores, and even 

 passing over our land without a halt, how is it that the 

 ordinary man sees so little of the game ? 



True, we have all beheld the swallows collecting on 

 roofs and telegraph wires, preparatory to their autumn 



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