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Shiavault - a Vault of Shia Islamic Books The Holy Quran Text. Translation & Commentary (the Example Commentary in Brief)(volume Three) More About the Birds (Almost all the birds are relatively light in weight, since weight is an important factor in the flight. Birds are short-lived creatures. Most of them mature at the end of their first year, are middle-aged when five years old, and die before they are ten years of age. Among the [ 491 ] exceptional birds, pigeon live to be 30 years old.

eagle 46 years, cockatoos 56, owl 68, parrot 80 years old. The body of bird is made streamlined, thus offering minimum resistance in the flight. Their head, neck, body, wings, and tail are covered with feathers, which provide protective covering, insulation and extremely light weight flight surface. Because their eyes are set on either sides of the head, birds can see better to the right and left than stright a head. Birds have no external ears so as to reduce the friction and resistance.

The ear opening in them is hidden by feathers. Their very flexible neck enables the bird to turn and look in all directions. Its tail acts as a rudder while in the flight, and as a ``brake'' on alighting. Birds are warm-blooded, and so they are able to maintain a constant body temparature of the environment. In this respect they differ from fishes. This warm-bloodness is made possible by the insulating body covering of feathers, and by a highly efficient circulating system.

A relative large four-chambered heart pumps the blood rapidly through the bird's body. Blood temparature ranges from 102³F to 112³F, and the heart beat from 200 to 1000 per minute, in different species and with varying activities. Birds require large quantities of food, and a rapid digestive process to maintain their high rate metabolism. Their digestive system is adapted to meet this needs.

Flight requires highly co-ordinated senses and muscles, and as might be expected, areas of birds brain controlling these functions are well developed. Bird's vision is exceptionally acute. Their eyes have unusual powers of accomodation, changing rapidly from near to far vision, an ability which serves them well in flight through the branches of trees. Birds also have color vision.

Some birds are strightly herbivorous, some are carvivorous, but the majority are omnivorous varying their [ 492 ] diet with the seasonal availability of food.