XXX INTRODUCTION. 
penters, and without the aid of any other chisel than their 
wedged bills. 
But the most consummate ingenuity of ornithal architecture 
is displayed by the smaller and more social tribes of birds, who, 
in proportion to their natural enemies, foreseen by Nature, are 
provided with the means of instinctive defence. In this labor 
both sexes generally unite, and are sometimes occupied a week 
or more in completing this temporary habitation for their 
young. We can only glance at a few examples, chiefly domes- 
tic ; since to give anything like a general view of this subject 
of the architecture employed by birds would far exceed the 
narrow limits we prescribe. And here we may remark that, 
after migration, there is no more certain display of the reveries 
of instinct than what presides over this interesting and neces- 
sary labor of the species. And yet so nice are the gradations 
betwixt this innate propensity and the dawnings of reason that 
it is not always easy to decide upon the characteristics of 
one as distinct from the other. Pure and undeviating in- 
stincts are perhaps wholly confined to the invertebral class of 
animals. 
In respect to the habits of birds, we well know that, like 
quadrupeds, they possess, though in a lower degree, the capa- 
city for a certain measure of what may be termed education, 
or the power of adding to their stock of invariable habits the 
additional traits of an inferior degree of reason. Thus in those 
birds who have discovered (like the faithful dog, that humble 
companion of man) the advantages to be derived from asso- 
ciating round his premises, the regularity of their instinctive 
habits gives way, in a measure, to improvable conceptions. In 
this manner our Golden Robin (/eerus baltimore), or Fiery 
Hang Bird, originally only a native of the wilderness and the 
forest, is now a constant summer resident in the vicinity of 
villages and dwellings. From the depending boughs of our 
towering elms, and other spreading trees, like the Oriole of 
Europe, and the Cassican of tropical America, he weaves his 
pendulous and purse-like nest of the most tenacious and dur- 
able materials he can collect. These naturally consist of the 
