Thursday, February 28, 2013
INTRODUCTION
Birds are ‘warm-blooded’
vertebrates, with fore-limbs modified to wings, and skins covered with feathers.
Vertebrates are characterised by having a spinal column and a skull. ‘Warm
blooded’ or homoiothermic (constant temperature) means that their body
temperature is kept more or less constant and above that of their surroundings.
Typically, the forelimbs as wings give birds the power of flight although there
are some flightless birds. In some cases (e.g. penguins and puffins) the wings
are used for swimming under water.
All birds reproduce by laying eggs
which are fertilised internally before laying.
The skull and lower jaw are
extended forward into mandibles which make a beak.
The bird's legs and toes are
covered with overlapping scales.
Birds possess a third, transparent
eyelid, the nictitating membrane, which can move across the eye.
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