20 INTRODUCTION. 
countries the art has reached a higher development. 
The purpose of the nest is merely to secure the safety 
of the eggs and young, and it is not quite clear why 
such very different methods should be pursued to 
accomplish this rather simple matter. A strong cup- 
shaped nest, inconspicuously placed, would seem to 
be all that is necessary ; but instead of this, we have _ 
long pendent nests on the terminal ‘twigs of elm- 
trees, and showy nests on slight shrubs, even some- 
times decked out with bits of newspaper. There are 
swallows that build clay houses on the outside of 
bridges or barns where everybody can see them, in- 
stead of placing them in the nooks and corners where 
they would be concealed even from that arch-villain, 
nobody’s cat. Some birds will hollow out a deep 
cavity in the sound wood of a healthy tree, when 
next door there is a natural hollow in dead wood, 
just as warm, as capacious, and as safely situated ; 
and the great crested flycatcher advertises his home 
by hanging a snake-skin where the door-knob ought 
to be, if he had use for one. 
There have been many learned essays written about 
birds’ nests and a variety of conclusions reached, but 
it is, after all, much a matter of theory. Had there 
been good field ornithologists in the earliest days of 
bird-life and the record of the race kept until the 
dawn of history, a great deal would be intelligible 
now that must forever remain a mystery. But there 
is one important fact of which we must not lose sight : 
the fashions are slowly changing. There is one bird 
we call a “chimney-swallow,” but these birds were 
about before the first chimney was built, and so lived 

