10 THE FIRST BOOK OF BIRDS 
rootlets, and pull narrow strips of bark off the 
grapevines and the birch-trees, or they pick up 
strings and horsehairs, and many other things. 
Robins and swallows use mud. 
As they go on building, the mother bird gets 
inside and turns around and around to make it 
fit her form, and be smooth and comfortable for 
her to sit in. 
When a nest is made, it must be lined. Then 
some birds go to the chicken yard, and pick up 
feathers, and others find horsehairs. Some of 
them pull off the soft down that grows on 
plants, or get bits of wool from the sheep pas- 
ture, or old leaves from the woods, and make it 
soft and warm inside. 
Some bird homes are only platforms, where 
it seems as if the eggs must roll off, and others 
are deep burrows, or holes in the ground, where 
no one can get in. Some are dainty baskets 
hung between two twigs, and others are tiny 
cups of felt with lichens outside. 
Kach species of bird builds in its own way. 
There are as many different ways to make nests 
as there are kinds of birds to make them. 
Then after all the trouble birds have taken to 
build a nest, they seldom use it a second time. 
If a pair have two broods in a season, they 
almost always build a new one for each family. 
