Many eggs that are laid in holes or other dark places are white without markings of any kind, as illustrated by those of the Chimney Swift, Belted Kingfisher, and all Woodpeckers. In such instances Nature shows no disposition to be lavish with her colouring matter where it is not needed.
Behaviour When Nest Is Discovered.—After the young are hatched it is even easier to find nests by watching the parents. The nestlings are hungry at all hours, and the old ones are visiting the nest at frequent intervals throughout the day. Birds behave very differently when their nests are discovered. A Cuckoo will glide away instantly and will make no effort to dispute your possession of her treasures. A Crow will also fly off, and so will a Wild Duck and some others. On the other hand, the Mockingbird, Robin, or Shrike, will raise a great outcry and bring about her half the birds of the neighbourhood to pour out on you their vials of wrath, unless you have the good judgment to retire at once to a respectful distance. Warblers will flit from bush to bush uttering cries of distress and showing their uneasiness. The Mourning Dove, Nighthawk, and many others will feign lameness and seek to lead you away in a vain pursuit. A still larger number will employ the same means of deception after the young have been hatched, as, for example, the Quail, Killdeer, Sandpiper, and Grouse.
However much a bird may resent your intrusion on the privacy of its sanctuary, it is very rare for one to attack you. I remember, however, a boy who once had the bad manners to put his hand into a Cardinal's nest and had a finger well bitten for his misdeed. Beware, too, of trying to caress a Screech Owl sitting on its eggs in a hollow tree; its claws are very sharp, and you will need first-aid attention if you persist. Occasionally some bird will let you stroke its back before deserting its eggs, and may even let you take its photograph while you are thus engaged. On one occasion I removed a Turkey Vulture's egg from beneath the sitting bird. It merely hissed feebly as I approached, and a moment later humbly laid at my feet a portion of the carrion which it had eaten a short time before—a well-meant but not wholly appreciated peace-offering.
Lessons to Be Learned.—An infinite variety of interesting things may be learned by watching birds at their nests, or by a study of the nests themselves. How many persons have ever tried to answer seriously the old conundrum: "How many straws go to make a bird's nest?" Let us examine critically one nest and see what we find. One spring after a red squirrel had destroyed the three eggs in a Veery's nest which I had had under observation, I determined to study carefully its composition, knowing the birds would not want to make use of it again. The nest rested among the top limbs of a little brush-pile and was just two feet above the ground. Some young shoots had grown up through the brush and their leaves partly covered the nest from view. It had an extreme breadth of ten inches and was five inches high. The inner cup was two and one-half inches deep, and measured the same across the top. In its construction two small weed stalks and eleven slender twigs were used. The latter were from four and one-half to eight inches long. The main bulk of the nest was made up of sixty-eight large leaves, besides a mass of decayed leaf fragments. Inside this bed was the inner nest, composed of strips of soft bark. Assembling this latter material I found that when compressed with the hands its bulk was about the size of a baseball. Among the decaying leaves near the base of the nest three beetles and a small snail had found a home.
The Veery, in common with a large number of other birds, builds a nest open at the top. The eggs, therefore, are often more or less exposed to the Crow, the pilfering Jay, and the egg-stealing red squirrel. This necessitates a very close and careful watch on the part of the owners. At times it may seem that the birds are not in sight, and that the eggs are deserted; but let the observer go too near, and invariably one or both old birds will let him know of their presence by voicing their resentment and sending abroad their cries of distress.
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 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 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. 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.
