BIRDS : perfect adaption to flight

 Perfect adaptation to flight :

    Almost every part of a bird's body has been transformed during evolution to give it optimal flight ability. Its wings and plumage are, of course, essential in enabling it to stay in suspension in the air and overcome gravity. Most birds are also aerodynamic in shape and their body weight is concentrated in the center to give them good overall balance. Their bones are pneumatized (hollowed out with air-filled cavities) to make them lighter, and most are welded together, preventing heavy joints and unnecessary muscles. Flight muscles are large and powerful, but their functioning requires a lot of oxygen, hence specific lungs designed to extract maximum oxygen from the air.

What is a feather?

    Feathers are made of fine, light fibers of keratin, the protein that covers the beak. Flight feathers and rectrices have a rigid central stem, the rachis, and hundreds of lateral filaments, the barbs. These are hung between them barbs forming a flat and aerodynamic surface.

The different feathers :

    The most important feathers for a bird are those of its wings (flight feathers) and tail (rectrices), because they are used to fly. Most of the lift necessary for flight is provided by the primary flight feathers (about 10 on each wing) and the secondary flight feathers (9 to 12) on the outer part of the wing. The other parts of the body are covered by the small contour feathers (coverts), which give the bird an aerodynamic profile, and by the down whose plummules are a good thermal insulation.

Skeleton :

    The skeleton of a bird resembles the skeleton of man in general terms but is totally different from it in its details. Birds have only three fingers on their "hand", which serves as a support for flight feathers. The wing pivots at shoulder level, while the elbow and wrist only allow horizontal movements to fold or unfold the wing. The tail skeleton is just a stump. Each rib has a hook-shaped process that rests on the next rib to strengthen the strength of the rib cage. Finally, the powerful muscles of the flight fit on a huge bone, the keel.

How the wings work !

    The wings provide support for the bird in two ways :

> When it flaps its wings to fly, the air is pushed backwards and downwards, ensuring progression and elevation in the air.

 > Once the bird has gained speed, its wings "welcome" the action of the wind like the sails of a boat, which accentuates the thrust and lifting force.

Flight regulation :

    The flight is easier when the air is moving fast. If this is too slow, vortices form around the wings and the lift drops suddenly: the bird comes to a stop, loses its balance and falls. Slow-flying birds (such as eagles) use the spread primary flight feathers (the tip of their wings) as additional "mini-wings" which improve flight stability.

The respiratory system :

    The bird's lungs are much more efficient than ours. The direction of air in our bronchi is reversed depending on whether we breathe in or out. Since our lungs do not completely empty, there is stale air left after each breath. In birds, air flows in one direction through the lungs through a complex system of air sacs distributed throughout the body. Clean air continually enters the lungs, expelling stale air and providing a large oxygen ratio.

Plumage hygiene :

    The tiny barbs that form a flat, smooth surface can collapse and lose their parallelism. Birds therefore realign their barbs with their beaks. Most also lubricate their feathers to make them waterproof thanks to the oil secreted by a gland in their rump. Some even bathe in puddles or dust to maintain their plumage.

Pneumatic bones !

    If you've ever picked up a dead bird, you know how light that animal's bones are. But did you know that its feathers weigh three times as heavy as its skeleton? If his bones are so light and so strong, it is because they contain a network of air-filled cavities reinforced by struts.