334 HOMING WITH THE BIRDS 



In a final summing up of the migi-ation question, 

 I think that it is well proved that birds migrate 

 at the demand of a subconscious impulse, that they 

 know unerringly the line of travel to follow. Even 

 when hindered in low flight by the blinding lights 

 of cities and light-houses, or when turned from their 

 course by heavy winds, unless lost and driven until 

 they meet death, they continue their flight across 

 long stretches of land and water, arriving event- 

 ually at their destination. I think that it will be 

 agreed that for the most part birds that have 

 flocked and are really in the course of long migra- 

 tion are at least a mile above the surface of the 

 earth, often two or three miles. The low-flying 

 flocks are those which have collected near to us 

 and are not yet under headway, or strays and 

 weaklings from larger flocks. Also, I think that 

 it will now be conceded that the old idea of a bird's 

 being able to make a straight sweep of a thousand 

 miles in four or five hours is utterly out of the 

 question. Certainly, the whole subject needs 

 deeper investigation and more thorough study 

 than has yet been given to it; but when the best 

 that the human mind can do is summed up, it 

 will probably resolve itself into this, "The stork 

 in the heaven knoweth her appointed time" con- 

 cerning when birds migrate. Their speed in flight 

 can be determined. 



One comparison which irritates me is that be- 

 tween birds and humans to the detriment of the 



