bird wiki:
>For other uses, see Bird (disambiguation). Many - see section below. Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge Ostrich and Emu. Depending on taxonomic viewpoint, there are about 8,800â10,200 living bird species (plus about 120â130 that have become extinct in the span of human history) in the world, making them the most diverse class of terrestrial vertebrates.
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wing wiki:
>For some other uses of the word "wing" please see Wing (disambiguation). A wing is a surface used to produce an aerodynamic force normal to the direction of motion by travelling in air or another gaseous medium, facilitating flight. It is a specific form of airfoil. The first use of the word was for the foremost limbs of birds, but has been extended to include other animal limbs and man-made devices.
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