66 BIRDS’ NESTS. 
birds that nest in this manner resort to uninhabited 
islets and secure protection through isolation. 
Some birds nest alone, and jealously guard the vicin- 
ity of their home from the approach of other birds, 
generally of the same species. Others nest in colonies 
brought together by temperament or community of 
interests, and dwell on terms of the closest sociability. 
The material used by birds in building their nest, 
is as varied as the nature of the sites they select. The 
vegetable kingdom contributes much the largest share. 
Grasses, twigs, and rootlets are the standard materials ; 
but plant-down, plant-fibers, bark, leaves, lichens, clay, 
spiders’ webs, hair, fur, and feathers are also used, while 
in some cases a gummy secretion of the salivary glands 
furnishes a kind of glue. | 
Birds have been classified, according to the manner 
in which they employ these articles, as weavers, tailors, 
masons, molders, carpenters, felters, etc. 
Sometimes both sexes assist in the construction of the 
nest, or one bird collects the material while the other 
adjusts it. Again, the female performs the task alone, 
aided only by the encouraging voice of the male. 
The time of construction varies from one to two 
weeks to as long as three months in the case of the South 
American Ovenbird, who in June begins to build the 
nest it will not occupy until October. The Fish Hawk 
evidently believes in the value of a stick in time, and 
often repairs its nest in the fall. 
Lack of space prohibits a discussion of the influences 
which assist in determining the character of birds’ nests. 
They may be summarized as follows : 
First, necessity for protection. 
Second, conditions imposed by locality. These affect 
both the site and material, as illustrated by Doves, who 
nest in trees in wooded countries and on the ground in 
