Transcript Birds
Birds Birds Birds What is a bird? Birds are reptile-like animals that maintain a constant internal body temperature. Birds have an outer covering of feathers; two legs that are covered with scales and are used for walking or perching; and front limbs modified into wings. What is a bird? Feathers separate 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. Feathers Feathers come in a variety of shapes, sizes, and colors. Feathers The two main types of feathers are contour and down. Feathers Barb Contour feather: Contour feathers provide the lifting force and balance needed for flight. Down feather: Down feathers trap air close to the body and keep the bird warm. Barbule: The hooks on each barbule fit together, holding them flat. Evolution of Birds Paleontologists agree that birds evolved from extinct reptiles. Embryos of birds and reptiles 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. Evolution of Birds Archaeopteryx was the first birdlike fossil discovered. Archaeopteryx looked like a dinosaur, but it had feathers. 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. Archaeopteryx 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. Evolution of Birds Dinosaurs Modern reptiles Modern birds Ornithischia (bird-hipped dinosaurs) Saurischia (lizard-hipped dinosaurs) Ancestor of dinosaurs Reptile ancestor Archaeopteryx 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 Body Temperature Control Birds generate their own body heat and are called endotherms. Endotherms have a high rate of metabolism. Metabolism produces heat. Feathers insulate a bird enough to conserve most of its metabolic energy, allowing it to keep warm. Feeding Birds need to eat a lot of food to produce the heat energy they need to maintain metabolism. Feeding Birds’ beaks, or bills, are adapted to the type of food they eat. Insect-eating birds have short, fine bills that pick ants and insects off leaves and branches, or can catch flying insects. Seed-eaters have short, thick bills. Carnivorous birds shred their prey with strong hooked bills. Feeding Long, thin bills gather nectar or probe mud for worms and shellfish. Large, long bills pick fruit from branches. Long, flat bills grasp fish. Beak Adaptations Coevelution Feeding 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. Feeding Esophagus Crop When a bird eats, food moves down the esophagus and is stored in the crop. Feeding In some birds the crop has a second 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. Feeding 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. Feeding The muscular walls of the gizzard squeeze the contents, while small stones grind the food. Gizzard Respiration Birds have a highly-efficient way of taking in oxygen and eliminating carbon dioxide. Air enters air sacs. It flows through the lungs where gas exchange takes place. Respiration 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. 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. Bird Heart Domestic pigeon Heart 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. Response Birds have well-developed sense organs, which are adaptations that enable them to coordinate the movements required for flight. Response Birds have well-developed eyes which allow them to see color very well. Most bird species can hear quite well. Taste and smell are not well developed in most birds. Movement Some birds, such as ostriches and penguins cannot fly. Most birds, however, can fly. The skeletal and muscular systems of flying birds exhibit adaptations that enable flight. Movement Vertebra Skull Collarbone (wishbone) Pelvic girdle Strut Tailbone Pectoral griddle Air space Sternum Rib cage Movement 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. Movement Bones are strengthened by struts. Air spaces make bones lightweight. Reproduction Both male and female reproductive tracts open into the cloaca. Mating birds press their cloacas together to transfer sperm from male to female. Reproduction 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 on its bill. Once the bird has hatched, it rests for a while and lets its feathers dry. Groups of Birds There are nearly 30 different orders of birds. Approximately 20 of those orders are represented in Ohio The largest order of birds is the passerines, or perching birds. New World Vultures Order: Ciconiiformes Example: Turkey Vulture Characteristics: - Moderately hooked beak; long, broad and rounded wings; raptorial feet; head of adults is without feathers Foraging Technique: high soaring (uses thermals) Food: carrion Habitat: open lowland, avoids heavily forested regions Turkey Vultures Diurnal Birds of Prey Eagles, hawks, falcons, etc. Order: Falconiformes Examples: Osprey, Bald Eagle, Red-tailed Hawk Characteristics: - Strongly hooked beak; long and usually broad wings, raptorial feet Foraging Technique: low patrol, swoops Food: fish, birds, small mammals Habitat: coasts – rivers, large lakes Bald Eagle Birds of Prey Swifts and Humming Birds Order: Apodiformes Examples: Chimney Swift, Ruby-throated Hummingbird Characteristics: - long, flat, pointed wings, brilliant metallic colors (hummingbird) Foraging Technique: hover gleaning Food: nectar and insects Habitat: Deciduous or mixed woodland forests; open areas with scattered trees Ruby-throated Humming Bird Woodpeckers Order: Piciformes Examples: Pileated Woodpecker, Red-headed Woodpecker, Northern Flicker Characteristics: - strong, usually straight, chisel-like or pointed beak; moderately long wings; strong zygodactyl feet; decurved and very pointed nails Foraging Technique: bark gleaner Food: insects; Fall – nuts, fruits, acorns, sap Habitat: deciduous/coniferous forest; open woodland Woodpeckers 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.