Birds are vertebrate animals adapted for flight.
Many can also run, jump, swim, and dive. Some, like penguins, have lost the ability to fly but retained their wings. Birds are found worldwide and in all habitats. The largest is the nine-foot-tall ostrich. The smallest is the two-inch-long bee hummingbird.
Everything about the anatomy of a bird reflects its ability to fly. The wings, for example, are shaped to create lift. The leading edge is thicker than the back edge, and they are covered in feathers that narrow to a point. Airplane wings are modeled after bird wings.
The bones and muscles of the wing are also highly specialized. The main bone, the humerus, which is similar to the upper arm of a mammal, is hollow instead of solid. It also connects to the bird’s air sac system, which, in turn, connects to its lungs. The powerful flight muscles of the shoulder attach to the keel, a special ridge of bone that runs down the center of the wide sternum, or breastbone. The tail feathers are used for steering.
Birds have a unique digestive system that allows them to eat when they can—usually on the fly—and digest later. They use their beaks to grab and swallow food. Even the way a bird reproduces is related to flight. Instead of carrying the extra weight of developing young inside their bodies, they lay eggs and incubate them in a nest.
The fossil record shows that birds evolved alongside the dinosaurs during the Jurassic period 160 million years ago. The best known fossil is archaeopteryx, which was about the size of a crow.
bird, (class Aves), any of the more than 10,400 living species unique in having feathers, the major characteristic that distinguishes them from all other animals. A more-elaborate definition would note that they are warm-blooded vertebrates more related to reptiles than to mammals and that they have a four-chambered heart (as do mammals), forelimbs modified into wings (a trait shared with bats), a hard-shelled egg, and keen vision, the major sense they rely on for information about the environment. Their sense of smell is not highly developed, and auditory range is limited. Most birds are diurnal in habit. More than 1,000 extinct species have been identified from fossil remains.
Since earliest times birds have been not only a material but also a cultural resource. Bird figures were created by prehistoric humans in the Lascaux Grotto of France and have featured prominently in the mythology and literature of societies throughout the world. Long before ornithology was practiced as a science, interest in birds and the knowledge of them found expression in and stories, which then crystallized into the records of general culture. Ancient Egyptian hieroglyphs and paintings, for example, include bird figures. The Bible refers to Noah’s use of the raven and dove to bring him information about the proverbial Flood.
Various bird attributes, real or imagined, have led to their symbolic use in language as in art. Aesop’s fables abound in bird characters. The Physiologus and its descendants, the bestiaries of the Middle Ages, contain moralistic writings that use birds as symbols for conveying ideas but indicate little knowledge of the birds themselves. Supernatural beliefs about birds probably took hold as early as recognition of the fact that some birds were good to eat. Australian Aborigines, for example, drove the black-and-white flycatcher from camp, lest it overhear conversation and carry the tales to enemies. Peoples of the Pacific Islands saw frigate birds as symbols of the Sun and as carriers of omens and frequently portrayed them in their art. The raven—a common symbol of dark prophecy—was the most important creature to the Indians of the Pacific Northwest and was immortalized in Edgar Allan Poe’s poem “The Raven.” Eagles have long been symbols of power and prestige in many parts of the world, including Europe, where their representations are often seen in heraldry. Native Americans sprinkled eagle down before guests as a sign of peace and friendship, and eagle feathers were commonly used in rituals and headdresses. The resplendent quetzal—the national bird of Guatemala, which shares its name with the currency and is a popular motif in art, fabric, and jewelry—was worshipped and deified by the ancient Mayans and Aztecs. Highly symbolic birds include the phoenix, representing resurrection, and the owl, a common symbol of wisdom but also a reminder of death in Native American mythology. The bird in general has long been a common Christian symbol of the transcendent soul, and in medieval iconography a bird entangled in foliage symbolized the soul embroiled in the materialism of the secular world.
Highly symbolic birds include the phoenix, representing resurrection, and the owl, a common symbol of wisdom but also a reminder of death in Native American mythology. The bird in general has long been a common Christian symbol of the transcendent soul, and in mediev .@AKR7BIRDS