Birds and Birding's Guide to:

Watching THE ANATOMY OF BIRDS

Bird Wings

In the Bat the four fingers of the hand are greatly lengthened for the support of the membrane forming the wing; in the flying reptile (Fig. 7) the membrane is supported wholly by the enormously developed fifth or little finger.

In the bird the bones of the hand are lessened in number and peculiarly modified for the attachment of feathers which form the highest type of wing. The general characteristics of a bird's skeleton are lightness, length of neck, very decided difference between the fore and hind limbs, and reduction in the apparent number of bones of the hand and foot (metacarpals and metatarsals) by their fusion with one another.

The skull joins the neck by a single condyle as in reptiles, and, also as in reptiles, the ankle joint is between the bones of the ankle and not between the leg and ankle as in mammals. The jaw is not attached to the cranium directly as in mammals, but by a free quadrate as in snakes and some extinct reptiles. In existing reptiles other than snakes the quadrate is fixed.

Many ribs of the chest cavity bear little processes directed upwards and backwards, termed uncinate processes, and these are found in all birds save the Screamers, although almost wanting in the Secretary bird. Outside the class of birds such processes occur only in that curious New Zealand reptile, the Hatteria, and, in cartilage only, in Crocodiles. So, in many important particulars the skeleton of a bird resembles that of a reptile, and this led Huxley to unite the two in a common superclass, Sauropsida.

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