Editing Anatomy (section)

=== Bird anatomy ===
{{main|Bird anatomy}}
[[File:Duerer wing of a blue roller.jpg|thumb|Part of a wing. [[Albrecht Dürer]], {{circa|1500–1512}}]]
[[Bird]]s are [[tetrapod]]s but though their hind limbs are used for walking or hopping, their front limbs are [[Bird wing|wing]]s covered with [[feather]]s and adapted for flight. Birds are [[endotherm]]ic, have a high [[metabolic rate]], a light [[skeletal system]] and powerful [[muscle]]s. The long bones are thin, hollow and very light. Air sac extensions from the lungs occupy the centre of some bones. The sternum is wide and usually has a keel and the caudal vertebrae are fused. There are no teeth and the narrow jaws are adapted into a horn-covered beak. The eyes are relatively large, particularly in nocturnal species such as owls. They face forwards in predators and sideways in ducks.<ref name=Dorit895>{{cite book |title=Zoology |url=https://archive.org/details/zoology0000dori/page/881 |url-access=registration |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=[https://archive.org/details/zoology0000dori/page/881 881–895] }}</ref>

The feathers are outgrowths of the [[epidermis (zoology)|epidermis]] and are found in localized bands from where they fan out over the skin. Large flight feathers are found on the wings and tail, contour feathers cover the bird's surface and fine down occurs on young birds and under the contour feathers of water birds. The only cutaneous gland is the single [[uropygial gland]] near the base of the tail. This produces an oily secretion that waterproofs the feathers when the bird [[personal grooming|preens]]. There are scales on the legs, feet and claws on the tips of the toes.<ref name=Dorit895/>