23 Functions of Feathers
http://askabiologist.asu.edu/content/23-functions-feathers
American Poultry Advocate,
Volume 18 September 1910 , Page 624
Feather of the Barred Pullet.
A Portrayal of the Defects of the Barred Plymouth Rock Pullet Feather in a Way That Will Delight Every Breeder of This Variety. The Proper Length, Width, and Barring of the Feather, Together With the Proper Spacing and Width of Bars Are Fully Explained. By S. T. DIVINIA, St. Joseph, Mo.
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The American Breeds of Poultry: Their Origin, History of ...
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Frank L. Platt - 1921 Pages 81 and 82
"Utility of the plumage. Plumage has a very practical aspect. It keeps the body warm and dry. Nature has not given better protection to any animal than she has given to birds in the form of plumage. These light feathers which a chicken carries on its body are an effective insulator of body temperature. One of the difficulties of the incubator manufacturers has been to build a box that would keep out cold as effectively as does the plumage of a hen setting on eggs. They have built double walls and padded them in between. The average man who builds a poultry house that his hens may have a decent place in which to live, is usually tempted to build the house tight that the hens may be warm. He fails to learn the lesson from the bird which he sees sitting on the twig of a tree, singing and happy, as he looks out of the house on Christmas morning across two feet of snow. That little bird has been out all night and the wind has blown and it has been cold, but it did not freeze or die, for is it not there on the twig, chirp and happy, singing its Christmas carol? Fowls, like birds, breathe all the way through their lungs into four pairs of air sacs (which are the bellows-like portion of their respiratory system) affording the very best possible opportunity for the oxygen of fresh air to combine with the blood and be carried to all parts of the body. One thousand pounds of chickens breathe from 2 to 2l/2 times as much air as the same weight of cattle, horses or men, according to F. H. King. Birds have a higher temperature. Therefore, do not shut the poultry up in a close hen house; consider the nature of the bird and its coat of plumage. This overcoat is of nature's best make, effective as an insulator of body temperature, a wonderfully woven fabric of beautiful color. Let us learn more about it. The secondary feather. Did you ever examine a feather on the under side? There is a little secondary feather at the base, called the after-shaft. The great feathers of the wing and tail are an exception. This after-shaft of the body plumage serves as "the underclothes." Dr. P. T. Woods has suggested that when hens are housed in open front poultry houses the after-shaft assumes larger proportions than where the birds are cooped in tight quarters. The downy part of the feather helps to keep the bird warm, the soft fluff holding more air than were the feather material closely knit into a smooth surface all the way down to the skin. The smooth surface, however, is better to shed rain and makes the better outer protection; it also permits birds in flight to pass through the air with the least resistance."