Page:Popular Science Monthly Volume 5.djvu/296

282 part; and the color of the reflected light depends upon the angle of the incident ray to the surface, and varies as the angle varies. In one direction of the incident ray, the light will be wholly absorbed, and, none being reflected, the surface will appear intensely black. It will readily be perceived that every movement of the bird produces more or less a change of color. Even the heaving of the breast, in breathing, sometimes produces perceptible changes.

The nests of humming-birds are curiously, skillfully, and quickly made. Most of them are formed of the down of the gigantic silk-cotton tree, or other vegetable fibres, worked into a sort of wadding or felt, and covered on the outside with particles of lichen, moss, webs of spiders, etc., the saliva of the bird being used to assist in holding the parts together. They are generally cup-shaped, or conical. Martin says: "In position, these nests are as different as imagination can conceive. Some are attached to the fork of a branch; others are bound to a waving twig enshrouded by foliage; others are pendent, attached to the extremity of the leaves of palms, flags, and other plants, overhanging water; others, again, build on rocks, hanging their nests by filaments to the sides of bold precipices; others hang their nests to the extremity of slender, pendent tendrils. Their eggs are two in number, white, but often, from their transparency, they display the color of the yolk, the shell appearing as if tinged with a blush of orange-red or pink. The eggs are a long oval, measuring, on the average, from three-eighths to one-half of an inch in length." Captain Lyon, writing from Gongo Soco, Brazil, says: "It may interest you to have an account of some young humming-birds, whose hatching and education I studiously attended, as the nest was made in a little orange-bush, by the side of a frequented walk, in my garden. It was composed of the silky down of a plant, and covered with small, flat pieces of yellow lichen. The first egg was laid January 26th, the second on the 28th, and two little creatures, like bees, made their appearance on the morning of February 14th. The old bird sat very close during the continuance of the heavy rain for several days and nights. The young remained blind until February 28th, and flew on the morning of March 7th, without previous practice, as strong and swiftly as the mother, taking their first start from the nest to a tree about twenty yards distant." The intense activity of humming-birds makes it necessary for them to have food containing nitrogen, which they get by feeding on insects. Honey furnishes proper food, or fuel, for the lungs, but it alone cannot form muscle, or give strength. They resemble the swifts in their powers of flight; the woodpeckers, in their means for darting out the tongue; and the sunbirds, in the metallic lustre of their plumage.

The ruby and topaz, or ruby-crested, humming-bird (Chrysolampis moschitus, Boié) derives its common name "from the color of its head and throat, the former being of a deep ruby tint, and the latter