Birds of the World : A Popular Account (Classic Reprint)

Excerpt from Birds of the World: A Popular Account

Temperature. - It is a generally recognized fact that the temperature of birds is normally very high, but, strange enough, exact data on the subject are not extensive. Recently Mr. A. Southerland undertook to ascertain the tempera ture of certain Ratite birds, and one of the most interesting incidental facts brought out is the demonstration of a progressive increase from the lower to the higher birds; that is, the forms of birds that are regarded as the lowest in the scale exhibit the lowest normal temperature, while between these and the more active and highly organized there is almost every gradation. This condition also pre vails at least to some extent among mammals. The Apteryx or Wingless Birds of New Zealand exhibit the lowest temperature thus far recorded among birds, the average of three individuals belonging to two species being C. Next to the Apteryx come the Emeus, Cassowaries, and Penguins, with an average normal temperature of 39° C. While the Tinamous examined Showed a range from C. To C., or an average of 406° C. (105° E), which brings them up to the lower limit of the range of temperature usual for ducks, game birds, etc. The common fowls when lifted quietly off their perches at night have a temperature of 406° C. (105° E), but when lifted by day from nests whereon they are brooding, their temperature averages C. (107° From these birds there is another decided advance when we come to the great groups of small and excessively active birds such as sparrows,,warblers, etc., their temperature ranging from 42° C. F.) to 44° C. With an average of perhaps 109° F., or fully ten degrees above that of man.

Feathers. - We may now advert to a consideration of the peculiar outer covering of birds; namely, the feathers. A normal feather (fig. 1) consists of a hollow transparent basal portion calledthe barrel, or calamus, continuous with which is the main shaft, or rachis, which is opaque, roughly quadrangular in cross-section, and filled with a pithy substance. The rachis is furrowed along its inner surface; that is, on the side next the body of the bird. From the rachis above the barrel arise a series of lateral branches, the barbs or rami, which in turn give rise to the barbules, and these to minute, often hooked processes, the barbicels (fig. It is by the hooking together of these processes that the web is produced and strength is given it to resist or act upon the air. Springing from the under side of the feather, in many cases, at the juncture of the barrel with the web-bearing portion, is a secondary feather, or aftershaft, as it is called.

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