BIRD HOMES 29 



A second group, including the phoebe, builds a new 

 nest each season, but may rear more than one brood 

 in the nest. A third group, which includes most of 

 our birds, builds a new nest each year and for each 

 brood when more than one is reared. 



Materials. Birds use a great variety of materials 

 in the construction of their nests. Among the more 

 common materials are dry grass, rootlets, small 

 twigs, and hair. Robins and barn swallows use mud. 

 The Baltimore oriole uses string, yarn, and hair. The 

 catbird uses strips of bark from the grapevine. The 

 house wren fills its nesting-cavity with small twigs. 

 The phcebe constructs its nest of mosses and mud. 

 Many nests contain materials which man has indi- 

 rectly furnished, such as strings, yarn, pieces of cloth 

 and of paper. 



The nest is usually lined with a finer, softer ma- 

 terial than that used in the foundation. The chip- 

 ping sparrow uses horsehair for a lining, and many 

 birds use a very fine plant down. The crested fly- 

 catcher almost invariably puts into its nest a cast- 

 off snake-skin. 



Shape. The shape of the nest of the robin and 

 chebec has been observed in a number of cases to be 

 moulded by the breast of the bird, which moves 

 round and round in the nest fitting it to the breast. 



The cavities which woodpeckers make are found 

 to agree in general shape. This cavity is not simply 

 a hole of uniform diameter, but it is somewhat flask- 



