102 FRIENDS WORTH KNOWING. 
of them. The situation varies as much as the birds them- 
selves. Trees, however, form the most common support: 
among the tip-top branches of them warblers fix their tiny 
cradles; to the outer drooping twigs of them orioles and 
vireos can swing their hammocks; upon their stout horizon- 
tal limbs the thrushes and tanagers may come and build; 
against the trunk, and in the great forks, hawks, and crows, 
and jays will pile their rude structures; and in the cracks 
and crannies, titmice, nut-hatches, and woodpeckers clean 
-out old holes, or chisel new, in which to deposit their 
eggs. But most of the large birds of prey inhabit lone 
crags, making an eyrie which they repair from year to year 
for the new brood. The ground, too, bears the less preten- 
tious houses of sparrows and larks, and the scattered eggs 
of sand-pipers, gulls, and terns; the marshes are occupied 
by rails, herons, and ducks; the banks of rivers are bur- 
rowed into by kingfishers and sand-martins; so that al- 
most every conceivable position is adopted by some bird 
or another, and its peculiar custom usually, thongh not by 
any means invariably, adhered to by that species. A curi- 
ous instance of change in this respect is shown by the two 
barn-swallows and the chimney-swallow, which, before the 
civilization of this country, plastered their nests in caves, 
and in the inside of hollow trees, as indeed they yet do in 
a 
