Common Ostrich: Topping the list at 156kg, the Common Ostrich is a remarkable runner, capable of sprinting at speeds of up to 70km/h in the savannahs of Africa.
Somali Ostrich: Reaching weights of up to 105kg, the Somali Ostrich is distinct from the common ostrich and is found in the Horn of Africa.
Southern Cassowary: Similar in weight to the Northern Cassowary, this species resides in New Guinea and Queensland, Australia, thriving in rainforests and savannah woodland.
Northern Cassowary: Weighing up to 58kg, the Northern Cassowary is a flightless bird native to New Guinea, where males undertake the task of incubating eggs.
Emu: The Emu, with a maximum weight of 55kg, is a tall bird found in Australia and is one of the four surviving members of the Casuariidae family.
Emperor Penguin: The iconic Emperor Penguin, weighing up to 46kg, treks long distances over ice in Antarctica to reach breeding colonies.
Greater Rhea: Surpassing 25kg in weight, the Greater Rhea is omnivorous and dwells in Argentina, Bolivia, Brazil, Paraguay, and Uruguay's grasslands.
Lesser Rhea: The Lesser Rhea, weighing up to 25kg, roams across Argentina, Bolivia, Chile, and Peru, famously studied by Darwin during his voyage on the Beagle.
Mute Swan: With a maximum weight of 22.5kg, the Mute Swan is found in Central and Northern Europe as well as Central and Eastern Asia, often inhabiting freshwater rivers.