ornithology

• Two-legged (bipedal) vertebrates Distinguished from other vertebrates by: • Feathers • filamentous, soft, flexible, light-weight structures • dead when functional – must be replaced regularly•

  Functions: thermoregulation and flight
• Birds are two-legged (bipedal) vertebrates
• Birds are distinguished from other vertebrates by feathers, which are filamentous, soft, flexible, light-weight structures
• Feathers are dead when functional and must be replaced regularly
• Functions of feathers include thermoregulation and flight
• Birds are also distinguished from other vertebrates by their bills, which are toothless and covered with a horny sheath
• Birds have a digestive system specialized to process unmasticated food
• The lack of teeth is likely a weight-reducing adaptation for flight
• Birds have a gizzard, which is the functional equivalent to mammalian teeth and is a muscular structure used to grind food
• Bird bones are lightweight, spongy, strutted, and hollow
• There is a fusion of bones to increase strength in the hand, head, pelvis, and feet
• Birds have uncinate processes, which are backward-curved projections on the ribs that strengthen the body wall
• The furcula (wishbone) compresses and rebounds like a spring as the wings beat
• Birds have an endothermic, a 4-chambered heart, and an efficient respiratory system
• The reproductive system of birds includes large, richly provisioned external eggs
• The reproductive system is reduced, for example, females have one functional ovary
• Skull articulates with the first neck vertebra by means of a single occipital condyle
• Simple middle ear with only 1 bone (stapes) mammals have 3
• birds and reptiles have nucleated red blood cells
• cursorial theory - running dinosaurs heldout arms to heighten leaping ability and catch insects • Could jump higher and help maintain balance
• arboreal theory - climbing dinosaurs heldout arms to control leapsfrom branch to branch• Gliding/parachuting
• • 2 hypothesis about how they evolved:• Feathers aided in flight – elongated, frayed scales may have enhanced gliding/parachuting • temperature regulation devices • Some say it acted as heat shield that allowed birds to be more active in hot environments • Others say – prevent heat loss (endothermic dinosaur ancestors)
• feathers are composed of beta-keratin (have some similarities to alpha-keratin which is found in skin of all vertebrates – but not in the same group of proteins)
• The beta-keratin found in feathers belongs to a special class of proteins characterized by a deletion in their molecular sequence
• shaft down the center with the flexible vane on either side
• • The shaft has two parts: • calamus (quill) – short, tubular base which stays attached to the follicle until it is molted • rachis – long, central shaft which supports the vein
• The feather vane is made up of hundreds of tiny parallel barbs branch off the rachis
• barbules branch off the barbs which have hooklets that hold the feather together
• • Further out, the vane is firm, compact, and closelyknit (pennaceous)• Used as an airfoil• Protects the undercoat• Sheds water• reflects/absorbs solar radiation• Used in visual and auditory communication
• At the base of the vane are soft, loose, fluffy barbs(plumaceous) used for insulation
• • Contour feathers – include typical body feathersand flight feathers• Wing feathers – remiges (remex)• Tail feathers – rectrices (rectrix)