The Skin

BrokenWing Chronicles
The Skin

The skin of birds is different from other animals in several ways. For one, only birds have feathers. Some birds have ornamental outgrowths, characterized by thickened skin that has many blood vessels. For example, some birds have a comb, a bright red vertical projection from the forehead and crown. Some birds also have wattles, which are naked folds of skin that hang down from the mandibles. Some birds have ear lobes, which are folds of skin, that may be red, white or purple. The snood, also called the frontal process, and is a distensible fleshy process arising on the head between the eyes and nostrils of the turkey. Turkeys also have caruncles, which are small protuberances of skin on the head and upper neck.

The skin of birds contains no sweat glands, so birds rely on evaporative cooling from the respiratory tract. The main gland of birds is the uropygeal gland, and is present in most birds and may be relatively large in some aquatic species. It is absent in the emu, ostrich, many pigeons, Amazon parrots, and the hyacinth macaw, for example. Another adaptation with avian skin is the brood patch, an area over the breast that becomes thickened, very vascular and the feathers are lost during the brooding period. These modifications promote the transfer of heat from the hen to her eggs.

There are seven types of feathers, the contour, semiplume, down, powder down, hypopenna, filoplume and bristle feathers. The contours cover the surface of the body, and arise from feather follicles. The follicle consists of a living part and a nonliving part. Growing feathers, or blood feathers, have an active blood supply until the feather is grown out completely. If a bird plucks out a feather from a follicle repeatedly, it my eventually destroy the living portion of the follicle, resulting in a follicle that can no longer grow a feather. Feathers molt out when a new feather is developing in the follicle and the old feather is then pushed out. Normally, a plucked feather will begin to regrow from the follicle immediately, but a cut feather will not be lost until it is molted out. Most birds replace all their feathers yearly, and this is a continuous process, however, some birds molt during a particular time frame (for example, after breeding season, or in the summer).

The skin of birds has distinct, well-defined tracts called pterylae that contain the feather follicles for contours. The bare spaces between the pterylae are called apteria.

BrokenWing

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When all is done that is asked of me and I can fly no higher, I pray this day his hand extends to welcome home a flier.