24 INTRODUCTION. 
between the plumage of their foe and the blue hea- 
-vyen above them studded with clouds, and passing on 
fearlessly, they fall an easy prey to his voracious ap- 
petite, while did the bird present a darker image 
against the sky, it would produce alarm, and the fish 
would hurry off to the protection of some overhang- 
ing bank, or dive into the depths below. 
The instincts of birds are in many respects very 
remarkable. What sagacity do they display in dis- 
cerning the proper time for performing their migra- 
tions! With what precision do they direct their 
course through the darkness of night! With what 
skill do they construct their nests! And with what 
tender affection do they provide for the wants and 
protection of their young! It has been observed of 
the House Wren and many other birds, that the same 
pair will return to the same spot for many successive 
seasons: that these little creatures should be able to 
designate in a journey of at least one thousand miles 
the precise spot where they have nestled the year be- 
fore, shows a degree of intelligence not always found 
even in man. 
The migration of birds is by no means the Jeast 
interesting part of their history. How often do we 
observe when looking out upon some bright morning 
of spring, that while the air seems laden with fresh 
odors, it also bears upon its bosom a soft aérial music, 
a sweet incessant warble, the song of thousands of 
merry little travellers fresh from the distant south! 
Each day for weeks in succession seems to bring new 
arrivals, until at last we welcome the tardy little 
