Birds have adapted themselves to an aerial mode of life

Birds have adapted themselves to an aerial mode of life:

Birds have evolved from reptiles during the course of evolution. It is on this account that the birds are sometimes referred to as glorified reptiles.

If we see the shape, structure and appearance of the body of birds, we see that every part, organ and organ system is modified for aerial mode of life.

The body is boat shaped and stream lined. This particular shape helps the birds to fly easily in the air. The stream lined body provides least resistance to the air.
The forelimbs are modified into wings. The wings help the birds to fly.
The bones are very light, they contain air sacs in them. This reduces the weight of the body and also make them strong and compact.
The joints in the bones are fixed, sutures are not visible, this means that bones cannot dislocate while flying.

Heart is large sized to meet the high requirement of oxygen used during flight and high metabolic rate.
Body temperature remains constant.
Brain highly developed. Centres of balance well developed. Sense of sight well developed, they can see the even small articles moving on the ground while flying in the air.
Air sacs present in bones and other parts of the body. These serve two purposes- they make the body light and also store air for respiration.
Breast bone is provided with keel for the attachment for the flight muscles.
Presence of feathers, overlapping the body. Feather make the body warm and they are also waterproof.
Tail feathers long fan like, these act like rudders for steering during flight and also for stopping during the flight.
Stomach able to store food grains.
One ovary and one oviduct absent. This reduces the weight of the body.