In most situations, the alula is held flush against the wing however, it can be manipulated. American Zoologist 40: 461-477.Adult bald eagle landing, showing the alula in action The integumentary morphology of modern birds – an overview. Pterylography and natural and experimentally induced molt in Clark’s Nutcracker. Which came first, the feather or the bird? Scientific American 208: 84-93. ![]() Pterylae and apteria of a Clark’s Nutcracker ( Nucifraga columbiana), ventral view (From: Mewaldt 1958). Source: Pterylae and apteria of a Clark’s Nutcracker ( Nucifraga columbiana), dorsal view (From: Mewaldt 1958). Most prominent in the herons and bitterns (family Ardeidae),īird Banding Program at Powdermill Nature Reserve) ![]() While many species have powderįeathers scattered within patches of normal down, they are They are the only feathers that grow continuouslyĪnd are never molted. Thought to aid in preening and waterproofing the otherįeathers. The barbs of powderįeathers disintegrate, providing a fine powder that is Is continuously growing and disintegrating, thusĬreating the powdery substance. (yellow feathers near the bottom of the photo that formĮgrets, & bitterns and the quill of the powder down While most other birds' feathers produce a small amount The presence of pterylae and apteria, and differences among birds in their shape and distribution, may (1) be adaptations for reducing the total weight of the feathering, (2) better accommodate the movements of the body and the feathers, and (3) aid in thermoregulation via loss of body heat from apteria (Stettenheim 2000). These include the: (1) alar tract, including primary and secondary flight feathers plus coverts, (2) caudal tract that includes the rectrices and coverts, (3) capital tract, including all feathers on the head, (4) spinal tract (or dorsal) that extends along the mid-dorsal line and includes the cervical, interscapular, dorsal, and pelvic regions see Figures below), (5) humeral tract that extends from where the leading edge of the wing meets the body over the dorsal surface to the trailing edge of the wing, (6) femoral tract located on the dorsal surface of the thigh, (7) crural tract located on the lower leg, and (8) ventral tract that includes cervical, sternal, and abdominal regions (see Figures below). On the other hand, a few species that utilize their tail feathers as part of their sexual display have more than 12: for example, ptarmigan (16), prairie chicken and Ring-necked Pheasant (18), male peafow and Blue Grouse (20)."Īlthough the shape and distribution of pterylae vary among different families and orders of birds, eight major pterylae or feather tracts can generally be identified. Hummingbirds, swifts, most cuckoos, motmots, and toucans have 10, some rails and grebes have 8, and a few very small tropical passerine birds have 6. ![]()
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