_Character of Material Used._--A wide variety of material is used by birds that build open nests. Cotton and feathers enter largely into the composition of the lining of a Shrike's nest. In Florida the Mockingbird shows a decided preference for the withered leaves and stems of life-everlasting, better known as the plant that produces "rabbit tobacco." The nest of the Summer Tanager is made almost entirely of grasses, the outer half being green, freshly plucked blades that contrast strikingly with the {29} brown inner layer with which the nest is lined. Many of the Thrushes make use of large flat leaves, and also of rags and pieces of paper. Robins stiffen their nests by making in them a substantial cup of mud, which, when dry, adds greatly to the solidity of the structure. On the island of Cape Hatteras there are many sheep, and many Prairie Warblers of the region make their nests entirely of wool. The most dainty structure built, in this country, by the bill and feet of birds, is the nest made by the Ruby-throated Hummingbird. When completed it is scarcely larger than an English walnut, and is saddled on a small horizontal limb of a tree, often many feet from the ground. It is composed almost entirely of soft plant fibres, fragments of spiders' webs sometimes being used to hold them in shape. The outer sides are thickly studded with bits of lichen, and practised, indeed, is the eye of the man or woman that can distinguish it from a knot on a limb. Although the Hummingbird's nest is exceedingly frail, there is nothing on record to show that {30} any great number of them come to grief during the summer rains. It is, however, not called upon for a long term of occupation. Within a month after the two white eggs are laid the young depart on their tiny pinions. Young birds that require a longer period for growth before leaving the nest are furnished usually with more enduring abiding places. {31} In the case of the Bald Eagle, the young of which do not fly until they are many weeks old, a most substantial structure is provided. [Illustration: Nest of the Ruby-throated Hummingbird]