Badminton birdies are conical feathery balls traveling between two players when hit by players' using their rackets.
Shuttlecock is unique in this aspect as it has a distinct shaped ball for playing unlike the spherical ones used for other sports, except probably American football.
Arranging the feathers of birds in a conical fashion, with one end of the feathers held firmly in a cork, while a thin leather coat surrounds the cork itself, produces badminton birdies. The feathers "fan out" on coming out of the cork and are held together in two or three places by interwoven threads, thereby holding the feathers together and lending stability to the birdie.
Badminton birdies are known so because unlike other racket sports where the ball merely travels on being hit, in shuttlecock, the birdies "fly". That is, because of the conical shape of the shuttlecocks, they have a high drag, reducing their speed to a great extent, allowing them to literally float before reaching the opponent.
Because of this property, although badminton is the fastest racket sports in the world today, it rapidly looses its speed in the air before reaching the opponent.
Because of its distinct shape, it is also vulnerable to strong breeze, tending to travel along its direction. For this reason, playing badminton outdoors is frustrating because your timing, shot selection and placement go awry with breeze. Hence, it is always played indoors in clubs, amateur and professional circuits.
The best quality birdies are manufactured using the left wing feathers of Chinese ducks. Because of regulations regarding their use, feathered shuttles are easily available and cheaper in Asian countries than in the West. Even in Asia, when there were recent outbreaks of bird flu, millions of birds died or subjected to culling (killing) to arrest the spread of the disease. This caused a temporary demand on the availability of feathered shuttles for some time.
Alternatively, shuttlecocks can also be made from plastics, called synthetic shuttlecocks. Here the cork portion remains the same but the "skirt" is made up of plastic. It is more durable than the feathered shuttlecock and consequently can last longer.
One more distinctive feature of plastic shuttlecocks is that, the skirt tends to fold inward when hit during playing. This tendency minimizes the drag on the shuttle. Therefore it allows the shuttle to travel faster in the air and reach the opponent quickly. This facilitates power play better than feathered shuttles.
All said and done, players of all levels favor feathered shuttles over synthetic ones because they feel better, have high drag and predictable travel through air and relatively lighter. In today's plastic conscious world, they are also environment friendly in that they are biodegradable.
Fancy shuttlecocks are also available. For example, there are glowing shuttlecocks present in the market today, which enable people to play badminton even in the nights. But, they are used just for fun and not for playing any serious level badminton in tour circuits.