ee 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 nests 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
