238 THE MIGRA TIOX OF BRITISH BIRDS 



which they have had no experience, of which they can 

 therefore have no knowledge, and would be lost to all 

 direction or locality. How rarely do we have any proof 

 of this. It is true migrants are repeatedly driven out of 

 their usual course by storms and fogs, and this abnormal 

 deflection from their proper route is fatal to vast numbers 

 of birds every year. Were birds endowed with this 

 mysterious inherited sense of direction, most of the 

 wonderful scenes at our lighthouses in spring and 

 autumn would never be witnessed at all. But the perils 

 of the journey are great and constant ; birds blunder to 

 an almost incredible extent ; lose their way or perish 

 every year in numbers that can only be described as 

 astounding ! 



Another very important condition of Migration which 

 is too often and too persistently ignored by the majority 

 of people is the altitude at w'hich it is undertaken. I 

 have already dwelt at considerable length upon this 

 subject in the Migration of Birds {conf. pp. 77-84), to 

 which I would again refer the reader. The advantages 

 of such lofty flight are very obvious. Let a person stand 

 on some moderately lofty hill, say 400 feet or so above 

 the level of the sea, and let him remark the vast area 

 of country over which his vision can extend. The more 

 he increases his altitude, the wider will become the view 

 — hills, valleys, and coast-lines spreading out before him 

 in one uninterrupted expanse. Birds flying along a 

 lofty course will readily recognize the various landmarks 

 that they and their ancestors have been in the habit of 

 passing for ages. A headland, a river valley, a wide 

 reach of sand or shingle, for instance, may mark the 

 spot where the sea-passage begins ; a lofty down, a 



