The world's largest bird is Voromobe Titan

For 60 million years the colossal, flightless elephant bird Aepyornis Maximus stalked the savannah and rainforests of Madagascar until it was hunted to extinction around 1,000 years ago. The specimen weighing an estimated 860 kg about the same as a fully grown giraffe. 

In the study, Hansford examined elephant bird bones found around the world. Until now, the largest-ever elephant bird was described in 1894 by the British scientist C W Andrews as Aepyornis Titan a larger species of Aepyornis Maximus. 

Hansford said his research proved titan was indeed a different species. But he also found that its bones were so distinct from other elephant bird specimens that Titan was, in fact, an entirely separate genus. The creature would have stood at least three meters (10 feet) tall, and had an average weight of 650 kg, making it the largest bird genus yet uncovered. 

Source: ET e-newspaper