"What does this great downward journey of autumn mean?" you ask. What is the necessity for migration among a class of birds that are able to find food in fully half of the annual range? Why do birds seek extremes for nesting sites? This is a question about which the wise men have many theories, but they are still groping. One theory is that once the whole country had a more even climate and that many species of birds lived all the year in places that are now unsuitable for a permanent residence. Therefore, the home instinct being so strong, though they were driven from their nesting sites by scarcity of food and stress of weather, their instinct led them back as soon as the return of spring made it possible.
Thus the hereditary love of the place where they were given life may underlie the great subject of migration in general and that of the Bluebird's home in particular.
The Bluebird
at Home.
Before more than the first notes of spring song have sounded in the distance, Bluebirds are to be seen by twos and threes about the edge of old orchards along open roads, where the skirting trees have crumbled or decaying knot-holes have left tempting nooks for the tree-trunk birds, with whom the Bluebird may be classed. For, though he takes kindly to a bird-box, or a convenient hole in a fencepost, telegraph pole or outbuilding, a tree hole must have been his first home and consequently he has a strong feeling in its favor.
As with many other species of migrant birds, the male is the first to arrive; and he does not seem to be particularly interested in house-hunting until the arrival of the female, when the courtship begins without delay, and the delicate purling song with the refrain, "Dear, dear, think of it, think of it," and the low, two-syllabled answer of the female is heard in every orchard. The building of the nest is not an important function,—merely gathering of a few wisps and straws, with some chance feathers for lining. It seems to be shared by both parents, as are the duties of hatching and feeding the young. The eggs vary in number, six being the maximum, and they are not especially attractive, being of so pale a blue that it is better to call them a bluish white. Two broods are usually raised each year, though three are said to be not uncommon; for Bluebirds are active during a long season, and, while the first nest is made before the middle of April, last year a brood left the box over my rose arbor September 12, though I do not know whether this was a belated or a prolonged family arrangement.
As parents the Bluebirds are tireless, both in supplying the nest with insect food and attending to its sanitation; the wastage being taken away and dropped at a distance from the nest at almost unbelievable short intervals, proving the wonderful rapidity of digestion and the immense amount of labor required to supply the mill inside the little speckled throats with grist.
The young Bluebirds are spotted thickly on throat and back, after the manner of the throat of their cousin, the Robin, or, rather, the back feathers are spotted, the breast feathers having dusky edges, giving a speckled effect.
The study of the graduations of plumage of almost any brightly colored male bird from its first clothing until the perfectly matured feather of its breeding season, is in itself, a science and a subject about which there are many theories and differences of opinion by equally distinguished men.
The Food of
the Bluebird.
The food of the nestling Bluebird is insectivorous, or, rather to be more exact, I should say animal; but the adult birds vary their diet at all seasons by eating berries and small fruits. In autumn and early winter, cedar and honeysuckle berries, the grape-like cluster of fruit of the poison ivy, bittersweet and catbrier berries are all consumed according to their needs.