“The top of the nest includes in its thickness the end of the branch from which it hangs, with the terminal twigs of that branch, which serve as framework for the nest’s vaulted roof, while the foliage projecting through the sides of the nest protects it with its shade. Finally, to secure greater firmness of support, a cordage of wool and hemp is passed around the branch and interlaced with the felt of the nest. The inside of this hanging habitation is lined with down of the finest quality from the poplar tree. “Are you acquainted with the troglodyte or, as it is more commonly called, the wren? It is the smallest of our birds, and it too is a master in the art of nest-building. Clothed in reddish brown, with drooping wing and upturned beak and tail, it is always frisking, hopping, and twittering,—teederee, teeree, teeree. Every winter it comes flying about our houses, frequenting the wood-pile, inspecting holes in the wall, and prying into the densest thickets. At a distance it might be mistaken for a small rat. “In summer it lives in the pathless woods. There, under the shelter of some big root that lies close to the ground and is covered with a thick fleece of moss, it builds a nest patterned after that of the swinging titmouse. Its materials are bits of moss, selected for the purpose of making the nest undistinguishable in appearance from that to which it is attached. The bird gathers these materials and works them into the shape of a large, hollow ball with a very small opening on one side. The interior is upholstered with feathers. “The magpie fixes its dwelling in the top of some lofty tree whence, as from an observatory, it can spy from afar the approaching enemy. At the juncture of a number of branching twigs that offer adequate support it plants its nest, constructed of interlacing flexible sticks with a floor of tempered earth. Fine rootlets, blades of grass, and a few tufts of down form the bedding for the prospective brood. “So far there is nothing to differentiate the structure from ordinary nests; but now we behold the exhibition of a special talent on the magpie’s part. The entire nest, and more particularly its upper part, is surrounded by a thick rampart, a sort of fortified enclosure composed of thorny twigs securely intertwined. One would take the whole thing for a shapeless mass of brushwood. Through this rampart, on the side that is most strongly defended, an opening is left of just sufficient size to admit of the mother’s entrance and exit. It is the only door to the aërial fortress.