“ss 
XIV MIGRATION 359 
they fly with a tail wind. And a saving of time is 
a saving of effort. The best evidence in favour of the 
beam-wind theory is of the kind given by Herr 
Gitke, who says that he has seen birds heading, not 
towards their destination, but in a different direction.) 
But how is it possible to know exactly for what point 
they wish to steer? And how can we penetrate to their 
motives? Birds have been seen zigzagging as they 
flew down an estuary, and this, it is said, had for its 
object the avoidance of a tail wind. Before such 
evidence can be accepted, we want careful observations 
as to the direction of the wind, and then we must 
consider whether there is not some other perfectly 
simple explanation of their zigzag course. Asa rule 
it seems that weather does not greatly affect migration. 
A great storm will, no doubt, sometimes prevent the 
progress of birds altogether. But the Puffin arrives 
here punctual almost to the day, and many other birds 
vary but little in the time of their coming, so that it is 
clear that they do not wait for some particular wind. 
Wings shaped for Long Flight—From far South to 
far North. 
Migrants whose two homes are widely separated have 
wings long and pointed as the necessary equipment 
for their arduous flights. Mr. Seebohm has taken our 
Great Reedwarbler and other birds of the same genus 
and shown how the form of the wing varies with the 
extent of the migration.” 
1 Die Vogelwarte Helgoland, p. 27. 
2 Siberia in Europe, p. 245. 
