The smallest and the largest birds in the world?

The smallest bird is the male bee hummingbirds (mellisuga helenae), which live in Cuba, weigh 0.056 ounces and are 2.75 inches in length. The bill and tail account for half of this length.

The largest and strongest living bird is the North African ostrich (Struthio camelus . Males can be up to 9 feet tall and weigh 345 pounds, and when fully grown the have one of the most advanced immune systems of any animal. South Africa was the first country to see the commercial potential of ostrich products - the creature are prized not only for their large soft white feathers and their meat but also for their skins, which are made into the strongest commercially available leather in the world. Ostrich farming is believed to have begun in the Karoo and Eastern Cape c. 1863. By 1910 there were more than 20,000 domesticated ostriches in the country, and by 1913 ostrich feathers were the fourth most important south African export product. Demand began to dry up soon afterwards, but there was an ostrich revival in the 1920's when farmers started to produce biltong ( dry strips of ostrich meat) commercially.

From the Guinness Book of Records

You can also see - Amazing Bird Records | birding .com (http://www.birding.com/birdrecords1.asp)

The largest bird is ALBATROSS .

I think ostrich is also very large in the non flying birds.

Smallest humming bird largest ostrich

Heaviest and tallest bird: Ostrich at maximum 156 kg (345 lb) and 2.7 m (9 ft)

Heaviest flying birth: Great Bustard at maximum 21 kg (46.3 lb)

Largest extinct bird: Dromornis stirtoni of Australia at 454 kg (1,000 lb) and 3 m (10 ft)

Tallest extinct bird: Giant Moa of New Zealand at 3.7 m (12 ft)

Greatest wingspan: Wandering Albatross at up to 3.63 m (11 ft 11 in)

Greatest wingspan of landbirds: Andean condor and Marabou Stork tied at 3.2 m (10.5 ft)

Wow what a complete answer, I would like to add that some smallest species are still unknown. As in there are some birds that need to be identified, ornithology is the study that has got lots of space for new identifiers... so a lot are to be discovered and named...