Number of Species

• There are over 9,000 species of bird living today. Between the years 1500 and 2009, 133 bird species have become extinct.
  
  

Rare and Common Species

• The domestic chicken is the most common species of bird. Among the rarest bird species is the Orange-necked Partridge, the Sudanese Red Sea Cliff Swallow and the Spix's Macaw.
  
  

Size

• Male Ostrich
  
  The ostrich is the largest living species of bird. Ostriches can be nine feet high and weigh 350 lbs. The smallest is the .056-oz. Bee Hummingbird.
  
  

Largest in Flight

• Kori Bustard
  
  While the Ostrich may be the largest living bird, Africa's Kori Bustard is the heaviest bird capable of flight, weighing in at over 40 lbs.
  
  

Human Threat

• It is humans that cause bird species to become extinct through hunting, destruction of bird habitats and the release of non-native species into a particular area. Over 2,000 bird species are considered to be endangered or threatened.