Copyright Pearson Prentice Hall 31-2 Birds Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What Is a Bird? What Is a Bird? Class Aves Nearly 10,000 modern species. Birds are reptile-like animals that maintain a constant internal body temperature. Birds have: outer covering of feathers 2 legs covered with scales, used for walking/perching front limbs modified into wings Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What Is a Bird? Feathers are the single most important characteristic that separates birds from all other living animals. Feathers are made mostly of protein and develop from pits in the birds' skin. Feathers help birds fly and also keep them warm. The two main types of feathers are contour and down. Some birds, like herons, that live on or in water also have powder down, which releases a fine powder to repel water. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall What Is a Bird? Feathers Barb Contour feather: Contour feathers provide the lifting force and balance needed for flight. Birds have different types of feathers that vary in structure and function. An outer covering of feathers is the main characteristic that sets birds apart from other animals. Barbule: The hooks on each barbule fit together, holding them flat. Down feather: Down feathers trap air close to the body and keep the bird warm. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evolution of Birds Evolution of Birds Paleontologists agree that birds evolved from extinct reptiles. Embryos of both develop within amniotic eggs. Both excrete nitrogenous wastes as uric acid. Bones that support the limbs, and other skeleton parts, are similar in both groups. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evolution of Birds Archaeopteryx was the first birdlike fossil discovered. Dates from the late Jurassic Period, ~150 mya Looked like a small, running dinosaur with well- developed feathers covering most of its body. It had teeth in its beak, a bony tail, and toes and claws on its wings. It may be a transitional species between dinosaurs and birds with characteristics of both groups. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Evolution of Birds Other fossil evidence leads some to hypothesize that birds and dinosaurs both evolved from an earlier common ancestor. The origin of birds is still not completely resolved. New fossils of ancient birds are being found all the time. Copyright Pearson Prentice Hall

Form, Function, and Flight Birds have a number of adaptations that enable them to fly, including: highly efficient digestive, respiratory, and circulatory systems aerodynamic feathers and wings strong, lightweight bones strong chest muscles Most birds have these characteristics, even though some cannot fly. Copyright Pearson Prentice Hall

Form, Function, and Flight Body Temperature Control  Birds generate their own body heat and are called endotherms. Endotherms have a high rate of metabolism compared to ectotherms (reptiles). Metabolism is the sum of chemical and physical processes that go on inside the body. Metabolism also produces heat. Feathers insulate a bird enough to conserve most of its metabolic energy, allowing it to keep warm more efficiently. A bird’s body temperature is ~41oC (or 105.8oF). Copyright Pearson Prentice Hall

Form, Function, and Flight Feeding  Any body heat that a bird loses must be regained by eating food. Birds need to eat a lot of food to produce the heat energy they need to maintain metabolism. Small birds lose heat relatively faster than large ones, so they must eat more relative to their body size. The phrase “eats like a bird” is misleading, because most birds are voracious eaters. Copyright Pearson Prentice Hall

Form, Function, and Flight Birds’ beaks, or bills, are adapted to the food they eat. short, fine bills that pick insects off leaves and branches or catch flying insects short, thick bills crack seeds carnivorous birds shred prey with hooked bills long, thin bills to reach into flowers or probe mud for worms and shellfish. Large, long bills used to pick fruits or long, flat bills for grasping fish. Copyright Pearson Prentice Hall

Form, Function, and Flight Birds do not have teeth and cannot chew. Many birds have specialized structures to help digest food. The crop is a structure at the lower end of the esophagus in which food is stored and moistened. Copyright Pearson Prentice Hall

Form, Function, and Flight In some birds, like pigeons, the crop has a 2nd function During nesting season, the crop produces a substance rich in protein and fat. Parents regurgitate this to feed their newly hatched young. This provides young birds with materials they need to grow. Copyright Pearson Prentice Hall

Form, Function, and Flight The form that the stomach takes depends on the feeding habits of the bird. Birds that eat meat or fish have an expandable area in which large amounts of soft food can be stored. Birds that eat insects or seeds have a muscular organ called the gizzard that helps in the mechanical breakdown of food by grinding it. Copyright Pearson Prentice Hall

Form, Function, and Flight First chamber of stomach Gizzard Moistened food passes to the stomach, a two-part chamber. Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Copyright Pearson Prentice Hall

Form, Function, and Flight First chamber of stomach Gizzard The first chamber secretes acid and enzymes. Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Copyright Pearson Prentice Hall

Form, Function, and Flight First chamber of stomach Gizzard The partially digested food moves to the 2nd chamber, the gizzard. Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Trace the path of food through the digestive system. Copyright Pearson Prentice Hall

Form, Function, and Flight The muscular walls of the gizzard squeeze the contents, while small stones grind the food. Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Gizzard Copyright Pearson Prentice Hall

Form, Function, and Flight As digestion continues, the food moves through the small intestine, where the breakdown of food is completed and food is absorbed. Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Copyright Pearson Prentice Hall

Form, Function, and Flight The large intestine then stores undigested waste until it is eliminated. Undigested food is expelled through the cloaca Birds have a number of adaptations that enable them to fly, including an efficient digestive system. Copyright Pearson Prentice Hall

Form, Function, and Flight Respiration   Birds have a highly-efficient way of taking in oxygen and eliminating carbon dioxide. Air enters air sacs. It flows through the lungs in a series of small tubes lined with specialized tissue, where gas exchange takes place. Copyright Pearson Prentice Hall

Form, Function, and Flight Air flows in a single direction. The one-way flow of air: constantly exposes the lungs to oxygen-rich air. maintains a high metabolic rate. provides efficient extraction of oxygen, which enables birds to fly at high altitudes where the air is thin. Copyright Pearson Prentice Hall

Form, Function, and Flight Circulation   Birds have four-chambered hearts and two circulatory loops. There is complete separation of oxygen-rich and oxygen-poor blood. Oxygen-poor blood from the body is pumped to the lungs. Oxygen-rich blood returns from the lungs and is pumped to the rest of the body. Copyright Pearson Prentice Hall

Form, Function, and Flight Bird Heart Pulmonary – pumps from right ventricle to lungs Systemic – pumps from left ventricle to body To keep blood moving rapidly, a bird’s heart beats quickly—from 150 to more than 1000 beats per minute!  Copyright Pearson Prentice Hall

Form, Function, and Flight Excretion   Excretion in birds is similar to that of most living reptiles. Nitrogenous wastes are removed from the blood by the kidneys, converted to uric acid, and deposited in the cloaca. Most of the water is reabsorbed, leaving uric acid crystals in a white, pasty form. Copyright Pearson Prentice Hall

Form, Function, and Flight Response   Birds have well-developed sense organs, which are adaptations that enable them to coordinate the movements required for flight. Copyright Pearson Prentice Hall

Form, Function, and Flight Birds’ brains can quickly interpret and respond to signals. It is relatively large for their body size. The cerebrum controls behavior such as flying, nest building, care of young, courtship, and mating and is quite large. Compared to reptiles, birds have an enlarged cerebellum that coordinates the movements of wings and legs.  Copyright Pearson Prentice Hall

Form, Function, and Flight The cerebellum coordinates the movement of the wings and legs; it is larger in birds than in reptiles. The medulla oblongata coordinates basic body processes such as the heartbeat. Birds have well-developed eyes which allow them to see color very well and therefore have sizable optic lobes. Most bird species can hear quite well. Taste and smell are not well developed in most birds, therefore the olfactory bulbs are reduced. Copyright Pearson Prentice Hall

Form, Function, and Flight Movement   Some birds, like ostriches and penguins, cannot fly. They get around mainly by walking, running, or swimming. Most birds, however, can fly. The skeletal and muscular systems of flying birds exhibit adaptations that enable flight. Copyright Pearson Prentice Hall

Form, Function, and Flight Skeletal System of a Bird Skull Vertebra Pelvic girdle Collarbone (wishbone) Strut Tailbone Pectoral griddle Like most of its anatomy, a bird’s skeleton is well adapted for flight, providing a sturdy attachment point for muscles. The long bones are exceptionally strong and light because of cross-bracing and air spaces. In strong flying birds, such as pigeons, the chest muscles may account for as much as 30 percent of the animal’s mass.  Air space Sternum Rib cage Copyright Pearson Prentice Hall

Form, Function, and Flight In flying birds, many large bones are fused together, making the skeleton rigid. These form a frame that anchors the muscles used for flight. Bones are strengthened by struts. Air spaces between the struts make bones lightweight. Birds have large chest muscles that power the upward and downward wing strokes necessary for flight. Muscles attach to a keel that runs down the front of an enlarged breastbone, or sternum. Copyright Pearson Prentice Hall

Form, Function, and Flight Birds move their wings in a circular pattern similar to rowing. On the downstroke, feathers are held together, and the wings move down and rotate forward. This pushes air down and back, providing lift and propelling the bird through the air. During the upstroke, feathers are opened to allow air to move through them , making it easier to move the wings upward. The wings bend up, moving closer to the body, and rotate backward. Copyright Pearson Prentice Hall

Form, Function, and Flight Reproduction    Both male and female reproductive tracts open into the cloaca. Sex organs often shrink in size when not breeding. Mating birds press their cloacas together to transfer sperm from male to female. Some male birds have a penis that transfers sperm to the female. In females, a single ovary produces an amniotic egg with a hard outer surface made of CaCO3. Copyright Pearson Prentice Hall

Form, Function, and Flight Bird lay amniotic eggs that have hard outer shells. Most birds incubate their eggs until the eggs hatch. When a chick is ready to hatch, it makes a hole in the shell with a small tooth-like structure on its bill called the egg tooth. Once the bird has hatched, it rests for a while and lets its feathers dry. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Groups of Birds Groups of Birds There are nearly 30 different orders of birds. The largest order of birds is the passerines, or perching birds, including over 5000 species. Other groups of birds include: pelicans, parrots, birds of prey, cavity-nesting birds, herons, and ostriches. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Ecology of Birds Ecology of Birds Birds interact with ecosystems and humans in many ways. Hummingbirds pollinate flowers. Fruit-eating birds disperse seeds in their droppings. Insect-eating birds catch insects, controlling populations. Food! Sport – hunting Pillows/coats – down feathers Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Ecology of Birds Many birds migrate long distances, usually seasonally. Some species use stars and other celestial bodies as guides. Others use a combination of landmarks and cues from Earth’s magnetic field. Magnetic sense: allows them to sense rotation of Earth; used for migration Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Diagram Labels: A = esophagus B = crop C = liver D = gizzard E = stomach F = intestine G = cloaca H = colon I = pancreas J = air sac K = kidney L = heart M = lung N = brain Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 31-2 A bird with a short, thick bill probably eats fish. seeds. insects. fleshy fruit. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 31-2 Archaeopteryx has characteristics of both modern birds and ancient birds. amphibians and reptiles. reptiles and modern birds. amphibians and modern birds. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 31-2 Which of the following bird adaptations is NOT associated with flight? bones with many hollow air spaces air sacs in addition to lungs gizzard contour feathers Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 31-2 The largest order of birds is the perching birds. birds of prey. pelicans and relatives. penguins. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 31-2 Which of the following birds assists in pollinating flowering plants? pelican hummingbird raptor heron Copyright Pearson Prentice Hall