Birds – Class Aves

Evolution and Classification Birds are Vertebrates of the Class Aves Warm blooded The study of birds is called Ornithology

Origin and Early Evolution Evidence from fossils and from studies of comparative anatomy indicates that birds evolved from reptiles Their features and their fragile hollow bones do not preserve well.

Archaeopteryx The fossil genus Archaeopteryx link between reptiles and birds, these mammals possessed characters of both reptiles and birds. Like reptiles it had a large skull with teeth, bones that weren’t hollow, claws on its forelimbs, and a long tail. Its strong legs and rounded wings indicated that it glided rather than flew

Characteristics of Birds Body covered with feathers Bones are thin and hollow A toothless, horny beak in present Endothermic The 4-chambered heart Amniote eggs are encased in hard, calcium-containing shells.

Endothermy Generate and regulate body heat internally Enables birds to inhabit both cold and hot climate Body temperature ranges from 40- 46 degrees Celsius.(104 – 113 degrees F) To help conserve body heat, birds fluff out there feathers to insulation. Birds have a 4-chambered heart that allows oxygen to be distributed with maximum efficiency. The heart will beat up to 150 to 1000X/minute.

Respiration To maintain body temperature bird’s breathe rapidly Air sacs in lungs bring in more oxygen One-way flow of air from air sacs to lungs.

Digestive and Excretory system Food passes from the mouth cavity straight to the esophagus. Enlargement of the esophagus called the crop stores and moistens food. In the first chamber, The proventriculus, gastric fluids begin breaking down the food. Then passes through the gizzard, a muscular organ that kneads and crushes the food

Excretory System The avion excretory system is also efficient and light weight The two kidneys filter a nitrogenous waste called uric acid from the blood  highly concentrated uric acid travels by ducts called ureters to the cloaca, where along with undigested matter from the intestines, it is excreted in a semisolid, usually white mass

Beaks and feet Hawks and eagles have powerful beak and clawed talons that help them capture and then rip their prey. Swifts have a tiny beaks that opens wide like a catcher’s mitt to share insects in midair. The feet of flightless birds, on the other hand are modified for walking and running

Skeletons and Muscles Combine lightness and strength Bones are thin and hollow Furculum (wishbone) fused collarbone that stabilizes bird in flight. Fused bones form a sturdy frame that anchors the powerful breast muscles during flight and supports the muscles when a bird is walking or at rest.

Skeleton The keeled sternum supports the large breast muscles The humerus, ulna, and radius, along with the pectoral girdle and the sternum, support the wing. Flight muscles (pectorals) are attached to wing & keeled sternum Muscles make up 50% of the birds body weight.

Classification Most taxonomist classify the nearly 9,000 species of Class Aves into 27 orders To classify birds into orders and families taxonomists most often use morphological evidence from beaks, feet, plumage, bone structure, and musculature.

Feathers Modified scales Function: lift for flight help conserve body heat Feathers are the single most important characteristic that separates birds from living reptiles and all other living animals. Made from proteins in pits in the bird’s skin.

Parts of a feather Follicles, shaft, two vanes, barbules. Barbules – have microscopic hooks that hold barbules together Birds preen their feathers to clean them & coat them with oil. Preen glands are oil glands located at the base of the tail.

Types of feathers Down feathers Soft and fluffy Cover body of babies Provide undercoat insulating adult birds

Countour Feathers: Flight Feathers Give streamline shape to body Provide coloration to adult birds Give additional insulation to body Flight Feathers Specialized contour feathers Found on wings & tail

Molting Birds shed or molt feathers periodically Usually in late summer between breeding & migration. Flight feathers are replaced Some birds molt before courtship

Order - Passeriformes Includes half of all bird species. “perching” birds Large rear toe to provide better grip on branches. Food: nectar, seeds, fruit & insects Examples: robins, blue jays, wrens, cardinals

Order - Apodiformes Small, fast flying birds. Tiny feet Long, slender beak Eat insects (sometimes in flight) or lap nectar from flowers. Examples – hummingbirds and swifts

Order - Columbioformes Plump-breasted Small head Short neck, legs, beak Slender bill Feed on fruit and grain Examples – pigeons and doves

State Bird of Alabama Yellowhammer Northern Flicker