Birds have hollow bones so that they are lighter and have less weight pulling them down. Their bones act like the struts or girders (supports) of an airplane. Even though they are light, bird bones are strong enough to stand the stress of constant take-offs and landings.

Feathers are streamlined, light, strong, and extremely flexible to allow birds to move in the air.  Feathers can bend and twist open like venetian blinds.  Birds can control and direct their flight with their feathers and ensure smooth take offs and landings.

Bird bodies, wings, and feathers are all aerodynamic (narrow and streamlined) to help minimize drag.  One feather can have a million individual parts that are supported by a hollow shaft that runs up the centre of the feather.  A feather's position can be adjusted precisely.  Each feather part (barbs and barbules) are interlocked in a way that blocks the passage of air, bends easily, and allows the bird to repair breaks on the surface of its wings.  These parts work together appropriately to make one individual feather.

In addition to all that, birds have specialized muscles below the wing that act like a compact centre of gravity to stabilize the bird's body.  The muscles act like a pulley to control bird wings and to maximize lift.

Tails are balancing mechanisms.  They provide stability and help birds change their flying direction.  Birds can raise their tails to zoom up.  They can drop their tails to stall.  They can move their tails from side to side.

Even more remarkable is the communication and navigation systems birds have.  Birds that fly in large flocks such as geese and starlings twist and turn faster than the blink of an eye with the precision of fighter pilots.  How do birds in a flock avoid collisions in the air? 

Other birds like Arctic terns navigate long distances across the planet between the poles, often facing bad weather many times in their lives.  Scientists are only beginning to understand how they do this.  All the systems in birds, even their efficient respiratory (breathing) system, work together to meet the challenges of flight.

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Bird	Overlap (Similarities)	Airplane
wings made of feathers	wings - thin and smooth	wings made of metal
lift and thrust from wings	streamlined shape to reduce drag	lift and thrust from engine and propellers
shoulder joints and wing muscles to achieve more lift	tail for stability	winglets, slats, and flaps to achieve more lift
change angle of wings and tail to change direction	hollow structure to reduce weight	elevators and ailerons to change direction
spread feathers, lower legs, and increase angle of approach to land		wing flaps and slats increase drag to land
specialized organs to navigate		specialized instruments to navigate