The Common Ostrich, with a maximum weight of 156kg, is found in the savannahs of Africa. Males of this species, Struthio camelus, can reach a height of 2.75m and are known for their incredible running ability, reaching speeds of up to 70km/h (43mph).
The Somali Ostrich, with a maximum weight of 105kg, is distributed in the Horn of Africa. Initially believed to be a subspecies of the common ostrich, it was confirmed as a separate species in 2014, known as Struthio molybdophanes.
The Southern Cassowary, also with a maximum weight of 58kg, is found in New Guinea and Queensland, Australia. This species inhabits rainforests, swamp forests, and savannah woodland, and can grow up to 170cm in length.
The Northern Cassowary, with a maximum weight of 58kg, is distributed in New Guinea. Like other species of cassowary, the Casuarius unappendiculatus is a flightless bird, and the male is responsible for incubating the eggs for nine months.
The Emu, found in Australia, has a maximum weight of 55kg. Adult emus can stand at 190cm tall, with the largest individuals reaching the maximum weight.
The iconic Emperor Penguin, with a maximum weight of 46kg, is distributed in Antarctica. Known for its height of up to 115cm, this species can trek up to 120km over ice to reach its breeding colony.
The Greater Rhea, a grassland-dwelling species known as Rhea americana, has a maximum weight of over 25kg and is found in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.
The Lesser Rhea, also known as Darwin's rhea, has a maximum weight of 25kg and is distributed in Argentina, Bolivia, Chile, and Peru. This species was studied by Charles Darwin during his second voyage on the Beagle.