The question of the world’s biggest bird does not have a single, simple answer because “biggest” can refer to three different measures: mass, height, or wingspan. The largest bird by weight and height is a flightless terrestrial giant, while the largest by wingspan is a master of aerial gliding over the oceans. Understanding avian size requires looking at these distinct categories, as the physical demands of flight impose strict limits on body size.
The Heaviest and Tallest Bird
The title for the largest living bird by both mass and height belongs to the Common Ostrich (Struthio camelus). Males can stand up to 9 feet (2.75 meters) tall, making them the world’s tallest bird. A large male Common Ostrich can exceed 320 pounds (145 kilograms), securing its place as the heaviest bird on Earth.
Their immense size is directly related to their inability to fly, as the loss of flight removed the aerodynamic constraints that limit other species. The ostrich developed powerful, long legs capable of sustaining sprints up to 43 miles per hour (70 km/h). The Emu, found in Australia, is the second tallest bird, reaching heights up to 6.2 feet (1.9 meters). The Southern Cassowary is considered the third heaviest, with males weighing up to 154 pounds (70 kilograms).
Largest Wingspan: The Masters of the Air
Measuring the distance from one wingtip to the other reveals a different champion, a bird adapted for gliding over the open ocean. The Wandering Albatross (Diomedea exulans) holds the record for the largest wingspan of any living bird species, regularly reaching up to 11 feet (3.4 meters). One specimen recorded a span of 11 feet 11 inches (3.63 meters).
This massive measurement is essential for their nomadic lifestyle, allowing them to employ dynamic soaring to travel vast distances. They use wind shear near the ocean surface to gain lift and glide for hours without flapping. The Andean Condor, with a wingspan of up to 10 feet 10 inches (3.3 meters), is a close runner-up and possesses the largest wing surface area of any raptor. The wingspan of the largest pelicans also rival the condor’s size, but the albatross remains the leader in linear span.
The Largest Birds that Can Fly
The largest birds capable of sustained, powered flight are much smaller than their flightless cousins, due to the physical limitations imposed by aerodynamics. The maximum body weight for a bird capable of horizontal powered flight is generally considered to be around 40 pounds (18 to 20 kilograms). Beyond this limit, the energy required to generate enough lift for takeoff becomes unsustainable for the bird’s musculature.
The title of the world’s heaviest flying bird is often contested between two species of bustard: the Kori Bustard (Ardeotis kori) and the Great Bustard (Otis tarda). Male Kori Bustards from Africa are robust, with confirmed specimens weighing up to 40 pounds (18.1 kilograms). The Great Bustard, found across Europe and Asia, also has males that can reach comparable weights. These powerful birds represent the limit of avian engineering for flight by mass, relying on a burst of intense power rather than effortless soaring.