Common Ostrich: The largest and heaviest of all flightless birds, with an average mass of 104 kg (229 lb) and maximum mass of 156.8 kg (346 lb), reaching an average length of 210 cm (6.9 ft).
Somali Ostrich: Similar to the Common Ostrich but slightly smaller, with an average mass of 90 kg (200 lb) and maximum mass of 130 kg (290 lb), and an average length of 200 cm (6.6 ft).
Southern Cassowary: A large flightless bird native to Australia and New Guinea, with an average mass of 45 kg (99 lb) and maximum mass of 85 kg (187 lb), reaching an average length of 155 cm (5.09 ft).
Northern Cassowary: Slightly smaller than its southern counterpart, with an average mass of 44 kg (97 lb) and maximum mass of 75 kg (165 lb), and an average length of 149 cm (4.89 ft).
Emu: Australia's iconic bird, with an average mass of 33 kg (73 lb) and maximum mass of 70 kg (150 lb), reaching an average length of 153 cm (5.02 ft).
Emperor Penguin: The tallest and heaviest of all penguin species, with an average mass of 31.5 kg (69 lb) and maximum mass of 46 kg (101 lb), reaching an average length of 114 cm (3.74 ft).
Greater Rhea: Found in South America, with an average mass of 23 kg (51 lb) and maximum mass of 40 kg (88 lb), reaching an average length of 134 cm (4.40 ft).
Dwarf Cassowary: The smallest species of cassowary, with an average mass of 19.7 kg (43 lb) and maximum mass of 34 kg (75 lb), reaching an average length of 105 cm (3.44 ft).
Lesser Rhea: Native to South America, with an average mass of 19.6 kg (43 lb) and maximum mass of 28.6 kg (63 lb), reaching an average length of 96 cm (3.15 ft).
King Penguin: The second-largest species of penguin, with an average mass of 13.6 kg (30 lb) and maximum mass of 20 kg (44 lb), reaching an average length of 92 cm (3.02 ft).2.