The largest living bird, Ostrich

 

The largest living bird, a member of the Struthioniformes, is the ostrich (Struthio camelus), from the plains of Africa and Arabia. A large male ostrich can reach a height of 2.8 m (9.2 ft) and weigh over 156 kg (345 lb). A mass of 200 kg (440 lb) has been cited for the ostrich but no wild ostriches of this massive weight have been verified. Eggs laid by the ostrich can weigh 1.4 kg (3 lb) and are the largest eggs in the world today.

 
The largest bird in the fossil record may be the extinct elephant birds (Aepyornis) of Madagascar, which were related to the ostrich. They exceeded 3 m (10 ft) in height and 500 kg (1,120 lb).^[3] The last of the elephant birds became extinct about 300 years ago. Of almost exactly the same upper proportions as the largest elephant birds was Dromornis stirtoni of Australia, part of a 26,000-year-old group called mihirungs of the family Dromornithidae. The largest carnivorous bird was Brontornis, an extinct flightless bird from South America which reached a weight of 350 to 400 kg (770 to 880 lb) and a height of about 2.8 m (9 ft 2 in). The tallest bird ever however was the giant moa (Dinornis maximus), part of the moa family of New Zealand that went extinct around 1500 CE. This particular species of moa stood up to 3.7 m (12 ft) tall, but weighed about half as much as a large elephant bird or mihirung due to its comparatively slender frame.
The second largest bird ever capable of flight was Argentavis magnificens, the largest member of the now extinct family Teratornithidae, found in Miocene-aged fossil beds of Argentina, with a wingspan up to 8.3 m (28 ft), a length of up to 3.5 m (11 ft), a height on the ground of up to 2 m (6.6 ft) and a body weight of at least 80 kg (176 lb). The largest bird capable of flight was Pelagornis sandersi, which had a wingspan of up to 24 feet.