Many of the birds we encounter in our day-to-day lives are tiny, often weighing just a few grams. But some species of bird are surprisingly large, reaching heights even greater than the tallest humans. Most of the largest birds in the world are flightless which allows them to have denser bones and heavier bodies. The largest bird in the fossil record may be the extinct Giant elephant bird (Aepyornis maximus) of Madagascar, whose closest living relative is the kiwi. Giant elephant birds exceeded 2.3 metres (7.5 ft) in height, and average a mass of 850 kg (1,870 lb)
The largest fowl was the Stirton’s mihirung (Dromornis stirtoni) of Australia, part of a group called mihirungs of the family Dromornithidae, Stirton’s mihirung exceeded 2.7 m (8.9 ft) in height, and average a mass of 500 kilograms (1,100 lb)
Ostriches
Ostriches are the largest living birds in the world, with an average mass of 104 kg and average length of 210 cm. They lay the largest eggs and hold the record for the fastest land speed of any bird, reaching speeds of 70 kmph.
Cassowaries
The southern cassowary have an average weight of 45 kg and are around 155 cm long. Southern cassowaries are found in north-eastern Australia, Indonesia and New Guinea. Northern cassowaries are slightly smaller with an average weight of 44 kg and average length of 149 cm. They are endemic to northern New Guinea.
Emus
Endemic to Australia, emus are the second tallest living birds in the world that can reach up to 190 cm tall. They weigh an average of 33 kg. Female emus are usually slightly larger than the males and have significantly wider rumps.
Penguins
Emperor penguins are endemic to Antarctica and are the tallest and heaviest of all living penguins weighing an average of 31.5 kg and measuring 114 cm in height. During breeding season male Emperor penguins lose up to 15 kg as they do not eat anything while they protect their eggs from extreme cold for more than 2 months.
Rheas
Greater rheas are flightless birds native to South America. Greater rheas have an average mass of 23 kg and an average length of 134 cm. One male and five females escaped from a farm in August 2000. They survived the winter and began breeding. It is estimated that there is now a population of about 250 birds which are considered domestic and therefore protected from hunting.
