The concept of the “biggest bird in history” is not straightforward, as “biggest” can refer to different measurements: wingspan, weight, or height. Each metric reveals a different record holder among ancient avian species. Understanding these dimensions provides insight into prehistoric avian gigantism and the environmental forces that shaped their evolution.
The Record Holders
Among the most impressive extinct flying birds, two species stand out for their exceptional dimensions. Argentavis magnificens is considered the heaviest flying bird known to science. Fossil evidence suggests this colossal bird weighed 70 to 72 kilograms (154 to 159 pounds) and stood 1.7 to 2 meters (5.6 to 6.5 feet) tall. Its wingspan was estimated to be between 5.8 and 8 meters (19 to 26 feet). This giant teratorn lived during the Late Miocene epoch, around 6 million years ago, and its remains have been unearthed in central and northwestern Argentina.
For the largest wingspan, Pelagornis sandersi holds the record, with a wingspan estimated between 6.1 and 7.4 meters (20 to 24 feet). This ancient marine bird, though lighter than Argentavis magnificens with an estimated weight of 21.9 to 40.1 kilograms (48 to 88 pounds), had wings nearly twice the size of the largest living flying birds today. Pelagornis sandersi soared over oceans 25 to 28 million years ago. Its fossils were discovered in South Carolina, unearthed during the expansion of the Charleston International Airport.
A Glimpse into Their World
The immense size of these ancient birds dictated unique adaptations for flight and survival. Scientists infer that Argentavis magnificens primarily employed soaring flight, relying on thermal air currents to stay airborne with minimal flapping. Its robust legs and large feet suggest it could walk with ease. This bird likely preyed on medium-sized animals or scavenged carrion across the open plains of the ancient South American pampas.
In contrast, Pelagornis sandersi was a marine bird, spending much of its life gliding over the ocean. Its relatively short, stout legs suggest it was not agile on land and probably launched itself into the air by hopping off cliff edges or running briefly into the wind. This species possessed unique bony, tooth-like projections along its beak, effective for grasping slippery prey like fish and squid. These adaptations allowed Pelagornis sandersi to exploit marine food sources across ancient global oceans.
The Evolutionary Drive for Gigantism
The evolution of such enormous flying birds was influenced by environmental factors and ecological opportunities. Abundant food sources, such as large game for scavengers like Argentavis or rich marine life for Pelagornis, supported the energy demands of large body sizes. The absence of large aerial predators also reduced selective pressure against increased size. In addition, atmospheric conditions, such as denser air or consistent wind patterns, provided favorable conditions for supporting heavy soaring flight.
Gigantism offered advantages, including increased foraging efficiency and reduced vulnerability to predators. However, immense size also presented physiological challenges, particularly regarding takeoff and the metabolic costs of maintaining such a large body. The development of highly efficient soaring flight, as seen in these giants, was a key adaptation that mitigated some of these challenges, allowing them to exploit vast ecological niches.
Comparing Giants: Past and Present
Beyond Argentavis magnificens and Pelagornis sandersi, the fossil record reveals other instances of avian gigantism. Extinct flightless birds, such as the elephant birds (Aepyornis maximus and Vorombe titan) of Madagascar and the giant moas of New Zealand, represent some of the heaviest and tallest birds ever. Among large extinct flying birds, other notable species like the terror birds (Kelenken) also existed, demonstrating a diverse range of large avian forms throughout history.
Compared to the largest living birds today, the scale of these prehistoric giants is striking. The wandering albatross, with the largest wingspan among extant birds at 3.65 meters (12 feet), is dwarfed by Pelagornis sandersi. Similarly, the common ostrich, the heaviest living bird at over 156 kilograms (346 pounds) and standing 2.8 meters (9.2 feet) tall, is flightless. Even the Andean condor, a large living raptor with a wingspan of 3.2 meters (10 feet), is smaller than Argentavis magnificens. These comparisons highlight the scale of prehistoric aviators.