MIGRA TION, 235 



the leader cleaves the air with a special outlay of strength^ 

 he every now and then drops into the rear in the easier line 

 of the wake, some other one taking up the task in front. 

 The European Storks are said to perform, every now and 

 then, the most beautiful evolutions on their way, after 

 which they move straight forward as usual. In heavy fogs 

 or dark nights birds fly low, and that often at their peril. 

 Not infrequently they lie over during weather especially 

 unfavorable. All such as take long and high flights prefer 

 the moonlight and the wind ahead. Wind in the rear is 

 very unfavorable. Not infrequently birds prefer to travel 

 under the leadership of the more experienced of their class. 



Very noticeable, indeed, is the effect of this regular 

 migration in any locality. Compute the probable number 

 of any one species, as the Bay-wingedSparrow, or the Balti- 

 more Oriole, for instance, contained in every square mile of 

 their summer habitat, and imagine the immense tidal wave 

 which, at the exact time for each species, moves along the en- 

 tire breadth of the line of march. The more brilliant varieties 

 everywhere appeal to the eye; and, as they reach their sum- 

 mer residence, each kind of the birds of song makes the air 

 more resonant with its peculiar melody. How the arrival 

 of any numerous species modifies the entire phase of a 

 rural district ! The field and orchard teem with a new and 

 happy life, and from the forest comes the finest of nature's 

 melodies. 



In Eastern North America, the birds migrate in greater 

 numbers and over a greater reach of country than in any 

 other part of the world; therefore, I am especially led to 

 inquire how this wonderful thing is accomplished. What 

 strange and mighty impulse is this which, inspiring the 

 breasts of such countless multitudes at the same moment, 

 carries them on through bitter storms and numberless perils 



