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Bird

From Encyc
Bird Diversity, showing many species of birds.

A bird is a type of warm-blooded vertebrate animal in the class Aves. Their distinguishing characteristics are that they are covered with feathers and their forelimbs have become wings (even on species that cannot fly).

Most birds can fly, but there are also aquatic and terrestrial species. The related species of birds known as penguins repurposed their wings for swimming. A number of species of bird made their way to Islands were they had no predators, and lost the ability to fly. The Dodo was a flightless bird most closely related to pigeons. A number of sub-Antarctic islands are home to flightless birds related to ducks, known as Rails. The Ostrich, Emu, Rhea, Cassowary, Kiwi, Tinamous and the extinct giant Moa, are ratites, long legged birds that lost the ability to fly tens of millions of years ago. Birds are now considered the only living dinosaurs.

There are approximately 11,200 recognized species of birds.[1] Birds are seen everywhere, including mountains, deserts, forests, and even the ice in the Arctic and Antarctica. Most bird species are seen in the tropical regions. Many birds from farther north migrate south in the autumn, stay in the south in the winter, and migrate farther north in the spring.

Physical Appearance

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The skeleton of the birds are extremely light, but the skeletons are strong. Many bones are hollow and are filled with air, which helps the birds fly in the sky. Birds do not have teeth, but they have strong beaks. Birds are covered in feathers, which helps them assist other birds, to stay warm, and to protect against water. Birds usually clean and maintain their feathers daily, but they use an oil, known as the coccygeal gland, to keep them waterproof.

Birds have a complex respiratory system with air sacs that apply oxygen even during rapid flight. Birds have excellent eyesight that even some birds can see from far away and can recognize objects from afar, even though their sense of smell is poorly developed. Many birds can produce a wide range of sounds or songs using their voice, which is generated in a specialized organ called the syrinx, which is also known as the lower larynx.[2]

Among many birds, the wandering albatross has the largest wingspan of up to 11.5 feet long, while the bird with the heaviest wingspan is the trumpeter swan, which weighs to about 37 pounds. Large flying birds have bones with air-filled cavities (called pneumatic skeletons) because their size is limited to physics. As birds grow larger, their weight increases faster than their wing area, which makes flight harder. For example, if a bird’s length doubles, its weight increases eight times, but its wing area only increases four times. During the Pleistocene Epoch, which is about 2.6 million to 11,700 years ago, a giant bird called Teratornis incredibilis had lived, and it had an estimated wingspan of about 16 feet, which is the largest of any flying bird, which is similar to a modern condor.[3]

Species of Birds

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Excluding extinct species, birds may be classified into the following orders:

References

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  1. ↑ https://www.britannica.com/animal/bird-animal
  2. ↑ https://uk.vikidia.org/wiki/%D0%9F%D1%82%D0%B0%D1%85%D0%B8
  3. ↑ https://www.britannica.com/animal/bird-animal
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