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The ostrich is the largest and heaviest living bird species. It can reach heights of up to 9 feet (2.7 meters) and weigh between 220 to 290 pounds (100 to 130 kilograms).
Similar in size to the common ostrich, the Somali ostrich is found in the Horn of Africa. It is slightly smaller than its cousin, with males typically reaching heights of 7 to 8 feet (2.1 to 2.4 meters) and weighing around 220 pounds (100 kilograms).
Found in New Guinea and parts of northern Australia, the southern cassowary is a large, flightless bird known for its distinctive casque or helmet-like structure on its head. It can reach heights of up to 5.9 feet (1.8 meters) and weigh over 130 pounds (60 kilograms).
Found in South America, the greater rhea is the largest bird species in the Americas. It can reach heights of up to 4.9 feet (1.5 meters) and weigh around 66 to 88 pounds (30 to 40 kilograms).
Smaller than the greater rhea, the lesser rhea is found in South America, primarily in Argentina, Bolivia, Chile, and Peru. It can reach heights of up to 3.6 feet (1.1 meters) and weigh around 55 pounds (25 kilograms).