Classes of domestic birds. There are three classes of domestic birds—poultry, pigeons, and cage birds. The poultry class comprises land and water birds and contains nine kinds—fowls, ducks, geese, turkeys, guineas, peafowls, pheasants, swans, and ostriches. The pigeon class has but one kind, the pigeon, which is the only aërial bird domesticated for economic purposes. The cage-bird class has as its most important representative the canary. The other birds of this class have never been popular in America.

The question of increasing the number of species of birds in domestication interests many people. There is a general impression among those not familiar with the commercial aspect of aviculture that many more species might be domesticated. While it is true that many birds capable of domestication have not been domesticated, there are few of these that would serve any purpose not better served by some species already domesticated. It will be shown as the different kinds and varieties of domestic birds are discussed that the most useful kinds are always the most popular, and that many others are kept principally as ornaments. The number of ornamental creatures that can be kept in domestication is limited, for as a rule animals, like people, must earn their living.

CHAPTER II
CHARACTERS AND HABITS OF BIRDS RELATED TO USE

Feathers. The feathers of a bird are the most highly developed form of protective covering in animals, serving other important functions in addition to the primary one. Compared with the hair of a mammal or the scale of a fish or of a reptile, a typical soft feather from the body of a bird is a very complex structure, partaking of the characters of both scales and hair. The fact that birds have scales and hair as well as feathers shows their relation to these other forms of animal covering. This is best observed on a fowl. The legs of a fowl are normally smooth, with scales on the front of the shank and on the upper surfaces of the toes. In feather-legged fowls the feathers appear first along the outer sides of the shanks and toes. As the number of feathers is increased they grow longer and more feathers appear, until in the most heavily feathered specimens the soft skin is covered and the scales are almost hidden.

The face of a fowl is normally almost bare, the skin being a bright red like the comb and wattles; but at a distance of a few feet we can usually see some very small, fine feathers on it, and if we examine closely we see in addition still finer growths—hairs. Among the body feathers of a fowl, too, are quite long hairs. These are most easily observed after a bird is plucked. They do not come out with the feathers, and are removed by singeing.

Structure of feathers. The smallest feather that to the naked eye appears as something more complex than a hair, looks like a little bunch of fuzzy filaments. This is called down.

In the next higher form of feather a small round quill appears with filaments protruding from it like the hairs in an artist's brush. Such a feather is called a stub feather, or simply a stub. The best place to find these is on the outside of the shank of a fowl with scantily feathered legs.

The first form of the complete feather is best observed either on the head of a fowl or at the hock joint. The feathers in these places are very small, yet complete. The round quill is lengthened into a shaft. Extending from each side of this shaft is a single row of filaments, called barbs, the edges of which, interlocked with little hooks, form the web of the feather. On other parts of the body of the bird the feathers are larger, but the general structure is always the same. The size and special structure of the feather are always adjusted to suit the part on which it grows or the service which it has to perform.

As the first function of the feathers is to keep the bird dry and warm, the body feathers are all soft as compared with the large stiff feathers of the wings and tail; yet as we look at the feathers on different parts of the body of a bird we notice differences in their structure, and also notice that the structure of a feather is not always the same throughout its length. On the exposed parts of the feathers of the neck, back, wings, and breast the web is perfect and the feathers overlap so closely that they present a smooth surface. Under the surface, especially next the skin, the barbs are not smoothly joined, but are fluffy. Thus the same feathers which present a hard, smooth surface to the weather provide a soft, warm garment next the skin. Under the wings and on the underside of the body the feathers are quite fluffy throughout their whole length.

Arrangement of the feathers. As you look at a living bird the feathers appear to grow on all parts of the body. When the feathers are removed from the bird you see that while the skin is nearly all rough, with the little elevations where the feathers were removed, there are quite large areas where the skin is perfectly smooth, showing that no feathers grew there. These places are bare because feathers on them would interfere with the movements of the bird. The feathers on adjacent parts give the smooth areas sufficient protection.

Decorative feather forms. The natural decorative forms of plumage are found mostly in male birds and consist of extraordinary developments of the plumage of the neck and back, where the male birds of some species always have feathers differing in form from the feathers on the same parts of the female. When a feather appendage not common to a species is developed on some varieties, as the crest and beard on fowls and the ruff on pigeons, both sexes have it. The most interesting feather decorations will be described particularly in the chapters on the species on which they occur.

Fig. 1. Brown Leghorn chick (one day old)

Color in feathers. While colors in the plumage are distributed very differently in different species of birds, often making combinations peculiar to a species, there is in all the same wonderful formation of patterns, that depends for its effect in a section upon some overlapping feathers being marked alike and others having a different marking; and for the effect in a single feather, upon adjacent barbs being now alike, now different, in the distribution of the pigment in them. The best common example of a pattern covering a series of feathers is found on the wing of a Mallard Duck or of a Rouen Duck. Interesting examples of the formation of patterns on a single feather may be found in the plumage of barred, laced, and penciled fowls, and also in the lacings on the body feathers of the females of the varieties of ducks mentioned. Perhaps the most interesting illustrations of this kind, however, are to be seen on the plain feathers of the guinea and the gorgeous tail of the peacock.

The pigment which colors the plumage may be found in soluble form in the quills of immature colored feathers. It is not conspicuous unless it is quite dark. In black fowls it is often so abundant that a part remains in the skin when the feathers are removed. After the pigment is deposited in the web of the feather the color is fast. Water does not affect it, but it fades a little with age and exposure. New plumage usually contains a great deal of oil, a condition which is most conspicuous in white birds, to whose plumage the oil gives a creamy tint. In colored birds the presence of a large amount of oil in feathers is