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• Reptile-like animals that have maintained a constant internal body temperature • Two legs covered with scales that are used for walking or perching • Front limbs modified into wings • Outer covering of feathers: made mostly of proteins and developed from pits in the birds’ skin • Contour feathers • Down feathers • Powder down feathers • A dinosaur with feathers • Archaeopteryx: first fossil found of an early bird-like animal • Looked like a small, running dinosaur with well-developed feathers • Unlike modern birds, it had teeth, a bony tail, and toes and claws on its wings • It is a transitional species between dinosaurs and birds Adaptations for Flight • Highly efficient: digestive system, respiratory system, circulatory system • Aerodynamic feathers and wings • Strong chest muscles • Endotherm: animal that generates its own body heat and controls its body temperature from within • Include birds, mammals and some other animals • High rate of metabolism compared to ectotherms • Metabolism produces heat • A bird’s feather’s insulate its body enough to conserve most of its metabolic energy • Any body heat that a bird loses must be regained by eating food • The more a bird eats, the more heat energy its metabolism can generate • Small birds must eat more, relative to their body size • Birds beaks, or bills, are adapted to the food that they eat • Crop: structure at the lower end of the esophagus in which food is stored and moistened • Gizzard: a muscular organ that helps in the mechanical breakdown of food • Air sacs: one of several sacs attached to a bird’s lungs into which air moves when a bird inhales; allows for the one-way flow through the respiratory system • Advantages: – The one-way flow of oxygen-rich air helps birds maintain their high metabolic rate – Enables birds to fly at high altitudes where there is little oxygen in the atmosphere • 4 chambered hearts and 2 separate circulatory loops • 2 ventricles • Complete separation of oxygenrich and oxygen-poor blood • This double-loop system ensures that oxygen collected by the lungs is distributed to the body tissue with maximum efficiency • Similar to that of many reptiles • Nitrogenous wastes are removed from the blood by the kidneys and converted into uric acid • Uric acid is sent to the cloaca • Water is reabsorbed into the body • Uric acid crystals leaving the body are in a white, pasty form • Well-developed sense organs to coordinate the movements required for flight • Brain can quickly interpret and respond to many incoming signals • Brain is large for its body • Well developed eyes • Can hear well • Sense of taste and smell are not well-developed; the olfactory bulbs in the brain are small • Some birds cannot fly • Walk: ostriches • Swim: penguins • Flying birds: many large bones are fused together to form a sturdy frame for flight • Both male and female reproductive tracts open into the cloaca • The sex organs are internal and often shrink inside when birds are not breeding • Amniotic eggs: similar to reptilian eggs but have hard outer shells •There are nearly 30 orders of birds •Some of the better known groups: • Perching birds: Passerines (includes songbirds such as larks, sparrows and finches) • Pelicans and their relatives • Birds of prey • Parrots • Cavity-nesting birds • Herons and their relatives • Ostriches and their relatives • Birds interact with the natural ecosystems and human society in many ways • Disperse seeds, pollinate plants • Migrate long distances • Serve as indicators of environmental health The earliest known bird, Archaeopteryx lithographica, lived about 150 million years ago during the Jurassic Period. Diversity Birds The world’s only wingless bird is the kiwi of New Zealand. A bird’s feathers weigh more than its skeleton does. Some of the 30 classes of birds: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Waterfowl (ducks, geese, swans) Perching birds, aka songbirds (sparrows, crows, cardinals) Gamebirds (chickens, turkeys, peacocks, pheasants) Woodpeckers & relatives The strike of the eagle Hummingbirds & swifts talon has Birds of prey (condors, twice the hawks, falcons, eagles) power of a Owls rifle bullet. Pigeons & doves Herons, storks, & relatives Parrots (macaws, lovebirds, cockatoos) Pelicans & relatives (cormorants, frigatebirds) Bald eagles have an Ostriches average wingspan Flamingos of 6 to 8 feet. Penguins The arctic tern makes the longest migration each year, flying 20,000 to 25,000 miles each year from the Arctic to the Antarctic and back again. Birds Vertebrates Common characteristics A hawk can see a mouse from a height of one mile. Some parrots must fly over 500 miles a day to forage for food. The only known poisonous bird is the pitohui from Papua, New Guinea Beak with no teeth Bipedal Forelimbs modified into wings Body covered with feathers Endothermic Highly efficient respiratory system Hard-shelled amniotic eggs Extremely diverse! The largest bird is the ostrich. Falcons can dive at over 200 mph. The Australian pelican has the longest beak in the world—up to 18.5 inches long! Feathers are unique to birds A bird’s heart beats 400 times per minute while resting and up to 1000 times per minute while flying.