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. [Illustration: Fig. 1. Brown Leghorn chick (one day old)]