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List of
Donors : |
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Birds
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Introduction
Birds are
feathered bipeds. They belong to class Aves and
subphylum Vertebrata. The most distinguishing character
of birds is the possession of feathers and the forelimbs
modified into wings. Birds descended 140 million years
ago from the reptilian stock similar to that which
produced dinosaurs, a bird-like creature, called
Archaeopteryx.
General
characteristics of bird
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Body
covered by feather, air-breathing, warm-blooded,
egg laying and bipedal flying vertebrates. |
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Body is more or less spindle-shaped and
divisible into head, neck, trunk and tail. Head
bears jaw bones prolonged into a toothless beak.
Neck is long and flexible. Trunk is compact and
tail is short and stumpy for balancing, steering
and lift during flight. |
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They
have one pair of legs and one pair of wings.
Legs are large and are adapted for walking,
running, scratching, perching, capturing food,
swimming etc. |
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Wing bears three clawless digits and leg bears
four clawed toes, of which the first or hallus
is directed backwards. |
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Body
is covered with feathers forming a
non-conducting body covering for warmth and
lightness of bodyweight. |
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The bones of birds are different to those of
other animals. They have a hollow space inside
the bone filled with air, which makes the body
light so that birds can fly easily. |
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Gullet dilated into a crop for quick feeding and
storage. Stomach is divided into a glandular
proventriculus and a muscular gizzard. |
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Heart is four chambered. |
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Lungs are spongy and non-distensible. Air-sacs
are present and some of them communicate with
air cavities in the bones. |
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Vocal cord is absent in birds but they produce
sound with the help of sound box (syrinx)
present at or near the junction of trachea and
bronchi. |
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Parental care is highly developed, ensuring
safety of the eggs and young. |
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